Protein Encyclopedia ①

Protein is an important component that composes all cells and tissues of the human body. Eating habits that consume more protein will have a greater risk of cancer. All the important components of the body need the participation of protein. Generally speaking, protein accounts for about 18% of the total mass of the human body, and the most important thing is that it is related to life phenomena.

Protein is the material basis of life, is an organic macromolecule, is the basic organic matter that constitutes a cell, and is the main bearer of life activities. There is no life without protein. Amino acids are the basic building blocks of protein. It is a matter closely related to life and various forms of life activities. Every cell and all important parts of the body have proteins involved. Protein accounts for 16% to 20% of the body weight, that is, an adult weighing 60 kg has approximately 9.6 to 12 kg of protein in his body. There are many types of proteins in the human body, with different properties and functions, but they are all composed of 20 kinds of amino acids (Amino acid) in different proportions, and they are constantly metabolized and renewed in the body.

Water solubility: insoluble

Composition: more than 20 amino acids

Structure: Level 1-Level 4

Formation method: dehydration condensation

Average molecular weight: The average molecular weight of 20 amino acids is 128

Basic meaning

Protein tetramer (quaternary structure)

Protein is a substance with a certain spatial structure formed by twisting and folding a polypeptide chain composed of amino acids in a "dehydration condensation" manner.

Protein must contain carbon, hydrogen, oxygen, nitrogen, and may also contain sulfur, phosphorus and other elements.

Protein is a polymer compound formed by combining α-amino acids in a certain order to form a polypeptide chain, and then combining one or more polypeptide chains in a specific way. Protein is the scaffold and main material that constitutes human tissues and organs. It plays an important role in human life activities. It can be said that without protein, there is no life activity.

The lack of protein in men requires more attention than the lack of protein in women. Once a man lacks protein, it will lead to a decline in male sperm quality, reduced sperm motility and non-liquefaction of sperm, resulting in male infertility

The structural formula of alpha amino acid

Protein is a complex organic compound, formerly known as "朊 (ruǎn)". Amino acids are the basic units that make up proteins, and amino acids are linked into peptide chains by dehydration condensation. Proteins are biological macromolecules composed of one or more polypeptide chains. Each polypeptide chain has 20 to hundreds of amino acid residues (-R); various amino acid residues are arranged in a certain order. The amino acid sequence of the protein is encoded by the corresponding gene. In addition to the 20 basic amino acids encoded by the genetic code, in proteins, certain amino acid residues can also be post-translationally modified to undergo chemical structural changes, thereby activating or regulating the protein. Multiple proteins can work together, often by joining together to form a stable protein complex, folding or spiraling to form a certain spatial structure, so as to perform a specific function. The organelle for the synthesis of peptides is the ribosome on the rough-faced endoplasmic reticulum in the cytoplasm. The difference of protein lies in the type, number, arrangement order and spatial structure of peptide chain.

The ingested protein is digested and hydrolyzed into amino acids and absorbed in the body to synthesize the protein needed by the human body. At the same time, the new protein is constantly being metabolized and decomposed, and it is always in dynamic balance. Therefore, the quality and quantity of food protein and the ratio of various amino acids are related to the amount of human protein synthesis, especially the growth and development of adolescents, the prenatal and postnatal care of pregnant and lying-in women, and the health and longevity of the elderly are all related to the amount of protein in the diet. close relationship. Protein is divided into complete protein and incomplete protein. Proteins lacking in essential amino acids or low in content are called incomplete proteins, such as those contained in cereals, wheat, corn and gelatin in animal skins and bones.

Related calculations

Atomic number

A protein molecule composed of m amino acids and n peptide chains contains at least n —COOH, at least n —NH2, m-n peptide bonds, and m+n O atoms.

Molecular mass

Suppose the average relative molecular mass of amino acids is a, containing b disulfide bonds, and the relative molecular mass of protein = ma-18(m-n)-2b

Gene control

Nucleotide 6 in the gene

Nucleotides in messenger RNA 3

Amino acids in protein 1

Composition and characteristics

Protein is composed of C (carbon), H (hydrogen), O (oxygen), and N (nitrogen). Generally, protein may also contain P (phosphorus), S (sulfur), Fe (iron), Zn (zinc), Cu (copper), B (boron), Mn (manganese), I (iodine), Mo (molybdenum), etc.

The composition percentage of these elements in protein is approximately: carbon 50%, hydrogen 7%, oxygen 23%, nitrogen 16%, sulfur 0~3% and other trace amounts.

(1) All proteins contain nitrogen, and the nitrogen content of various proteins is very close, with an average of 16%;

(2) Protein coefficient: For every 1g of nitrogen in any biological sample, it means that there are about 100/16=6.25g of protein. 6.25 is often called the protein constant.

the whole frame

Protein is a biopolymer composed of amino acids as the basic unit. The sequence of amino acids on protein molecules and the three-dimensional structures formed therefrom constitute the diversity of protein structures. Protein has a primary, secondary, tertiary, and quaternary structure, and the structure of the protein molecule determines its function.

Primary structure: The sequence of amino acid residues in the peptide chain of a protein is called the primary structure of the protein. Each protein has a unique and exact amino acid sequence.

Secondary structure: The peptide chain in the protein molecule is not linear, but is coiled (such as α-helix structure) or folded (such as β-sheet structure) to form a specific spatial structure. This is a protein The secondary structure. The secondary structure of the protein is mainly achieved by the hydrogen bond formed between the hydrogen atom on the imino (-NH-) of the amino acid residue in the peptide chain and the oxygen atom on the carbonyl group.

Tertiary structure: On the basis of the secondary structure, the peptide chain further forms a more complex tertiary structure according to a certain spatial structure. It is through this structure that myoglobin, hemoglobin, etc. make the cavity on the surface just hold a heme molecule.

Quaternary structure: The aggregate structure formed by the combination of polypeptide chains with tertiary structure in a certain spatial arrangement is called the quaternary structure of a protein. For example, hemoglobin is composed of 4 polypeptide chains with tertiary structure, two of which are α-chains and the other two are β-chains. The quaternary structure is similar to an ellipsoid.

connection method

Using about 20 kinds of amino acids as raw materials, the amino acid molecules are connected to each other into peptide chains on the ribosomes in the cytoplasm. The amino group of one amino acid molecule and the carboxyl group of another amino acid molecule are connected by removing a molecule of water. This combination is called dehydration condensation. Through the condensation reaction, the bond between the carboxyl group and the amino group that connects two amino acid molecules is called a peptide bond. Compounds formed by peptide bonds are called peptides.

Detection method

Add 3 ml of egg white diluent and water to the two test tubes of A and B respectively, and then add the biuret reagent A and B to the two test tubes in sequence. Observe the color change of the solution in the test tubes of A and B. The above demonstration experiment results show that the biuret reagent reacts purple with protein.

Metabolic absorption

Protein is initially hydrolyzed under the action of digestive enzymes in gastric juice, completing the entire digestion and absorption process in the small intestine. The absorption of amino acids is carried out by the active operation system through the small intestinal mucosal cells, transporting neutral, acidic and basic amino acids respectively. The protein digested and absorbed in the intestine comes not only from food, but also from the shedding of intestinal mucosal cells and the secretion of digestive juice. About 70g of protein enters the digestive system every day, most of which are digested and reabsorbed. The unabsorbed protein is excreted in the feces.

disease

excess

which performed

The kidneys have to excrete the protein they eat. When they break down the protein, they will produce a lot of nitrogen, which will increase the burden on the kidneys. Excessive intake of protein, especially animal protein, is also harmful to the human body. First of all, if you consume too much animal protein, you must consume more animal fat and cholesterol. Secondly, too much protein itself can have harmful effects. Under normal circumstances, too much protein must be deaminated and decomposed, and nitrogen is excreted from the body by urine, which increases the metabolic burden. Moreover, this process requires a lot of water, which increases the burden on the kidneys. If the kidney function is not good at all , The harm is even greater. Excessive animal protein intake also causes excessive intake of sulfur-containing amino acids, which can accelerate the loss of calcium in the bones and easily lead to osteoporosis.

harm

1. Once the protein is converted into fat in the body, the acidity of the blood will increase, which will consume a lot of calcium. As a result, the calcium stored in the bones is consumed, making the bones brittle.

2. The kidneys have to excrete the protein they eat. When they break down the protein, they will produce a lot of nitrogen, which will increase the burden on the kidneys.

Deficiency

Protein deficiency occurs in both adults and children, but children in the growth stage are more sensitive. The common symptoms of protein deficiency are decreased metabolic rate, decreased resistance to disease, and susceptibility to disease. The long-term effect is organ damage. The common symptoms are children’s growth retardation, malnutrition, decreased body weight, indifference, irritability, and anemia. As well as dry weight disease or edema, and secondary diseases due to easy infection. The lack of protein often coexists with the lack of energy, that is, protein-thermal malnutrition, which is divided into two types. One is a nutritional disease that basically satisfies the caloric intake but is severely insufficient in protein, which is called Gasika disease. The other is "weight loss", which refers to nutritional diseases in which protein and caloric intake are severely insufficient.

usefulness

1. Protein is an important raw material for building and repairing the body. The development of the human body and the repair and renewal of damaged cells are inseparable from protein.

2. Protein can also be broken down to provide energy for the life activities of the human body.

nature

Both sexes

Protein is a polymer compound composed of α-amino acids through peptide bonds. There are amino and carboxyl groups in the protein molecule. Therefore, similar to amino acids, protein is also an amphoteric substance.

Hydrolysis reaction

The protein undergoes a hydrolysis reaction under the action of acid, alkali or enzyme, and finally obtains a variety of α-amino acids after polypeptide.

When protein is hydrolyzed, the "breaking point" of the bond in the structure should be found, and the peptide bond is partially or completely broken during hydrolysis.

Colloidal properties

Some proteins can be dissolved in water (for example, egg white can be dissolved in water) to form a solution.

When the molecular diameter of the protein reaches the size of colloidal particles (10-9～10-7m), the protein has the properties of colloid.

precipitation

Reason: adding high concentration of neutral salt, adding organic solvents, adding heavy metals, adding alkaloids or acids, a small amount of salt (such as ammonium sulfate, sodium sulfate, etc.) can promote the dissolution of protein. If a concentrated inorganic salt solution is added to the protein aqueous solution, the solubility of the protein can be reduced and precipitated out of the solution. This effect is called salting out.

In this way, the salted out protein can still be dissolved in the water without affecting the properties of the original protein, so the salting out is a reversible process. Taking advantage of this property, the fractional salting-out method can be used to separate and purify proteins.

transsexual

Under the action of heat, acid, alkali, heavy metal salt, ultraviolet light, etc., protein will change in nature and coagulate. This kind of coagulation is irreversible and can no longer restore them to the original protein. This kind of protein change is called denaturation. After the protein is denatured, UV absorption, chemical activity and viscosity will increase and become easily hydrolyzed, but the solubility will decrease.

After the protein is denatured, it loses its original solubility and loses its physiological function. Therefore, the denaturation and coagulation of protein is an irreversible process.

Causes of protein denaturation

Physical factors include: heating, pressurizing, stirring, shaking, ultraviolet radiation, X-rays, ultrasonic waves, etc.:

Chemical factors include: strong acids, strong bases, heavy metal salts, trichloroacetic acid, ethanol, acetone, etc.

Color reaction

Protein can react in color with many reagents.

For example, if concentrated nitric acid is dropped into the egg white solution, the egg white solution will be yellow. This is due to the color reaction of protein (containing benzene ring structure) with concentrated nitric acid. It can also be tested with a biuret reagent, which produces a purple complex when it encounters proteins.

Odor response

When protein is burnt and decomposed, it can produce a special smell of burnt feathers. Use this property to identify proteins.

fold

The study of protein folding mechanism is of great significance for retaining protein activity, maintaining protein stability and folding and refolding of inclusion body protein. As early as the 1930s, Professor Wu Xian, a pioneer in the field of biochemistry in my country, explained the denaturation of proteins. Thirty years later, Anfinsen's classic research on ribonuclease A showed that unfolded proteins can be spontaneous in vitro Refolding is just that the sequence itself already contains all the information about the correct folding of the protein, and puts forward the thermodynamic hypothesis of protein folding. For this reason, Anfinsen won the 1972 Nobel Prize in Chemistry. This theory has two key points: (1) the state of the protein is in the balance between unfolding and the natural conformation; (2) the protein in the natural conformation is in the lowest energy state of thermodynamics. Although the amino acid sequence of the protein plays a central role in the correct folding of the protein, a variety of factors, including signal sequences, cofactors, molecular chaperones, and environmental conditions, will affect the folding of the protein. The new protein folds and assembles. Functional proteins are not all spontaneous. In most cases, they need the help of other proteins. Many folding enzymes and molecular chaperones involved in protein folding have been identified. The classic concept of protein "spontaneous folding" has changed and updated. But this is not in contradiction with the thermodynamic hypothesis of folding, but it completes the thermodynamic viewpoint in kinetics. In the process of protein folding, there are many forces involved, including some conformational steric hindrances, van der Waals forces, hydrogen bond interactions, hydrophobic effects, ionic interactions, entropy-driven folding caused by the interaction of polypeptides and surrounding solvents, but We still know very little about the specificity of the complex process of protein obtaining its natural structure. Many experimental and theoretical works are deepening our understanding of folding, but the problem is still unsolved.

In the research on the mechanism of folding, the early theory believed that folding is a gradual process from the denatured state to the intermediate state to the natural state, and conducted in-depth research on the folding intermediates. It is believed that the folding is carried out in a single way under the thermodynamic drive. of. Later studies have shown that there are a variety of experimentally measurable intermediates in the folding process, and the folding proceeds through a limited path. The new theory emphasizes that there is diversity in the initial stage of folding. The protein enters the folding funnel through many ways, so that the folding is described as a funnel-like image on the whole, and the kinetic process of folding is considered to be the partial folding of the protein as a whole. The progressive assembly of the protein, and with the changes of free energy and entropy, the protein finally finds its own correct folding structure. This theory is called the energy picture. The bumps under the funnel reflect that the protein conformation instantaneously enters the region of local free energy minimum.

A schematic diagram of the energy landscape. The height represents the energy scale, and the width represents the conformational scale. There are other low-energy states below the funnel, and the coexistence of protein types in different energy states is also minimized.

This theory believes that structurally homologous proteins can form similar natural conformations through different folding pathways. The amino acid sequences of human acidic fibroblast growth factor (hFGF-1) and salamander acidic fibroblast growth factor (nFGF-1) have about 80%. % Homology and structural homology (12 β-sheets are arranged in anti-parallel to form a β-sheet barrel). In the process of guanidine hydrochloride-induced unfolding, hFGF-1 can detect a melted sphere-like fold in the middle While nFGF-1 unfolds through two states (natural state to denatured state), no intermediates are detected. The kinetic studies of folding also show that the two proteins adopt different folding mechanisms. For the same protein, different osmotic pressure regulators are used, and the way of protein folding is also different, indicating that different osmotic pressure regulators have different stabilizing effects on the protein. Both of these examples illustrate the complexity of the folding mechanism and are consistent with the theory introduced above.

Physiological Function

Constructing the human body

Protein is the material basis of all life, an important part of the body's cells, and the main raw material for the renewal and repair of human tissues. Every tissue of the human body: hair, skin, muscles, bones, internal organs, brain, blood, nerves, endocrine, etc. are all made up of protein, so it is said that diet makes humans themselves. Protein is very important for human growth and development.

For example, the characteristic of brain development is the completion of cell proliferation at one time, and the growth of human brain cells has two peak periods. The first is when the fetus is three months old; the second is the period from birth to one year old, especially for babies from 0-6 months, when the brain cells grow violently. By the age of one year, the proliferation of brain cells has basically been completed, and its number has reached 9/10 of that of humans. Therefore, 0 to 1 year old children have unique requirements for protein intake, which is particularly important for children's intellectual development.

Structure substance

The human body is composed of tens of trillions of cells. Cells can be said to be the smallest unit of life. They are in the process of constant aging, death, and regeneration. For example, the epidermis of young people is renewed every 28 days, while the gastric mucosa is renewed in two or three days. Therefore, if a person's protein intake, absorption, and utilization are good, then the skin is shiny and elastic. On the contrary, people are often in a sub-healthy state. After tissue damage, including trauma, cannot be repaired in time and with high quality, it will accelerate the body's decline.

Carrier transportation

Maintain the normal metabolism of the body and the transportation of various substances in the body. The carrier protein is essential to maintain the normal life activities of the human body. Can carry various substances in the body. For example, hemoglobin—transports oxygen (red blood cell turnover rate of 2.5 million/second), lipoprotein—transports fat, receptors on cell membranes, and transporters. Maintenance and composition

Maintain the balance of osmotic pressure in the body: albumin. Maintain the acid-base balance of body fluids. It constitutes the neurotransmitter acetylcholine, serotonin and so on. Maintain the normal functions of the nervous system: taste, vision and memory.

Immunization of antibodies

There are white blood cells, lymphocytes, macrophages, antibodies (immunoglobulin), complement, interferon, etc. Update every seven days. When the protein is sufficient, this force is very strong, and when needed, it can be increased by 100 times within a few hours.

Enzyme catalysis

Various enzymes that constitute the necessary catalytic and regulatory functions of the human body. There are thousands of enzymes in our body, each of which can only participate in one biochemical reaction. Human cells undergo more than one hundred biochemical reactions every minute. Enzymes can promote the digestion, absorption and utilization of food. If the corresponding enzymes are sufficient, the reaction will proceed smoothly and quickly, and we will be energetic and not easy to get sick. Otherwise, the reaction will slow down or be blocked.

Hormonal regulation

It has the physiological activity of regulating various organs in the body. Insulin is synthesized from 51 amino acid molecules. Growth hormone is synthesized from 191 amino acid molecules (it has nothing to do with growth hormone).

Collagen

It accounts for 1/3 of the body's protein and generates connective tissue, which constitutes the body's skeleton. Such as bones, blood vessels, ligaments, etc., determine the elasticity of the skin and protect the brain (a large part of the brain cells are collagen cells, and form a blood-brain barrier to protect the brain)

Energy substance

Provide energy for life activities.

development path

Globular protein (tertiary structure)

The protein was discovered in 1838 by the Dutch scientist Gerrit Mard. He observed that living things cannot survive without protein. Protein is an extremely important macromolecular organic matter in the organism, accounting for 54% of the human body's dry weight. Protein is mainly composed of amino acids, and various types of proteins are formed due to different combinations and arrangements of amino acids. It is estimated that there are more than 100,000 kinds of proteins in the human body. Life is an advanced form of material movement. This way of movement is realized through protein, so protein has extremely important biological significance. The growth, development, movement, heredity, reproduction and other life activities of the human body are inseparable from protein. Life movement requires protein, and protein is also inseparable.

Protein post-translational transport

Some physiologically active substances in the human body, such as amines, neurotransmitters, peptide hormones, antibodies, enzymes, nucleoproteins, and proteins on cell membranes and in the blood that act as "carriers", are inseparable from proteins, which regulate physiological functions. Maintaining metabolism plays an extremely important role. The composition of muscles in the human motion system and the metabolism of muscles in the process of contraction, work, and completion of movements are all related to protein. Without protein, physical exercise is impossible.

In biology, protein is interpreted as a peptide formed by amino acids linked by peptide bonds, and then a substance formed by linking peptides together. It is easy to understand that it is the scaffold and the main material that constitutes the body's tissues and organs. Protein deficiency: Adults: muscle wasting, weakened body immunity, anemia, severe cases will produce edema. Minors: growth retardation, anemia, poor mental development, and poor vision. Excessive protein: Protein cannot be stored in the body, and the body cannot absorb too much. Excessive intake of protein will cause protein poisoning or even death due to metabolic disorders.

Classified information

The nutritional value of food protein depends on the type and quantity of amino acids, so it can be divided into three types: complete protein, semi-complete protein and incomplete protein according to the amino acid composition of food protein.

Complete protein contains a complete variety of essential amino acids, sufficient quantity, and appropriate proportions, which can not only maintain the health of adults, but also promote the growth and development of children, such as casein and lactalbumin in milk, ovalbumin and lecithin in eggs , Albumin and muscle protein in meat, soy protein in soybeans, gluten in wheat, gluten in corn, etc.

Semi-complete protein contains a complete variety of essential amino acids, but some amino acids are insufficient in quantity and in an inappropriate proportion, which can maintain life but cannot promote growth and development, such as gliadin in wheat.

Incomplete protein contains incomplete types of essential amino acids, which can neither sustain life nor promote growth and development, such as zein in corn, glial protein in animal connective tissue and skin, and legumin in peas.

Demand classification

Essential amino acids

The protein in food must be digested by the gastrointestinal tract and decomposed into amino acids before it can be absorbed and utilized by the human body. The human body’s need for protein is actually the need for amino acids. The absorbed amino acids can only meet the needs of the human body in terms of quantity and type, and the body can use them to synthesize its own protein. In nutrition, amino acids are divided into two types: essential amino acids and non-essential amino acids.

Essential amino acids refer to amino acids that cannot be synthesized by the human body or the synthesis speed cannot meet the needs of the human body and must be taken from food. For adults, there are 8 kinds of such amino acids, including lysine, methionine, leucine, isoleucine, threonine, valine, tryptophan, and phenylalanine. For babies, there are 9 types, one more histidine.

Non-essential amino acid

Non-essential amino acids do not mean that the human body does not need these amino acids, but that the human body can synthesize it or obtain it from other amino acids, not necessarily directly ingested from food. Such amino acids include glycine, alanine, serine, aspartic acid, glutamic acid (and its amines), proline, arginine, histidine, tyrosine, and cystine.

If the supply of some non-essential amino acids such as cystine and tyrosine is abundant, the required amount of methionine and phenylalanine among the essential amino acids can be saved.

Shape classification

In nutrition, food protein is divided into three categories according to the type and quantity of amino acids contained in food protein:

1. Complete protein This is a type of high-quality protein. They contain a complete range of essential amino acids, in sufficient quantities, and in an appropriate ratio to each other. This type of protein can not only maintain human health, but also promote growth and development.

2. Semi-complete protein Although this type of protein contains a complete range of amino acids, the quantity of some amino acids cannot meet the needs of the human body. They can maintain life, but they cannot promote growth and development.

3. Incomplete protein. This type of protein cannot provide all the essential amino acids needed by the human body. They can neither promote growth nor maintain life.

According to the shape of protein molecules, they can be divided into 3 categories

1. The molecular shape of globular protein is close to spherical, and the water solubility is good. There are many types and can perform a variety of biological functions.

2. The appearance of fibrous protein molecules is rod-like or fibrous, and most of them are insoluble in water. They are important structural components of organisms or protect organisms.

3. Membrane proteins are generally folded into a nearly spherical shape and inserted into the biomembrane, and some of them are bound to the surface of the biomembrane through non-covalent bonds or covalent bonds. Most of the functions of biological membranes are achieved through membrane proteins.

Structure type

Fibrous protein: a major type of water-insoluble eggs

White matter usually contains polypeptide chains with the same secondary structure. Many fibrin proteins are tightly bound, and provide mechanical strength for individual cells or the entire organism, playing a protective or structural role.

Globular protein: A type of protein that is compact, approximately spherical, and contains tightly folded polypeptide chains, many of which are soluble in water. The typical globulin contains depressions or fissures that can specifically recognize other compounds.

Keratin: A protein that is insoluble in water and plays a protective or structural role composed of parallel polypeptide chains in α-helix or β-sheet conformation.

Collagen (protein) (collagen): It is the most abundant protein in animal connective tissue. It is composed of procollagen molecules. Procollagen is a protein with a right-handed supercoil structure. Each procollagen molecule is formed by right-handed rotation of a polypeptide chain with 3 special left-handed helixes (pitch 0.95nm, each circle contains 3.3 residues).

Chaperone: It forms a complex with a newly synthesized polypeptide chain and helps it fold correctly into a protein with biological functional orientation. The chaperone protein can prevent the formation of incorrectly folded intermediates and the incorrect aggregation of unassembled protein subunits, assist in the transmembrane transport of polypeptide chains and the assembly and disassembly of large multi-subunit proteins.

Myoglobin (myoglobin): is a binding protein composed of a peptide chain and a heme prosthetic group. It is a protein that stores oxygen in the muscle. Its oxygen saturation curve is hyperbolic.

Hemoglobin (hemoglobin): is a binding protein composed of 4 subunits containing heme prosthetic groups. Hemoglobin is responsible for transporting oxygen from the lungs to peripheral tissues, and its oxygen saturation curve is S-shaped.

Protein denaturation (denaturation): The destruction of the natural conformation of biological macromolecules leads to the loss of their biological activity. When the protein is exposed to light, heat, organic solvents and some denaturants, the secondary bonds are destroyed, resulting in the destruction of the natural conformation and the loss of the biological activity of the protein.

Renaturation: Under certain conditions, the phenomenon that denatured biological macromolecules return to a biologically active natural conformation.

Allosteric effect (allosteric effect): also known as allosteric effect, is a phenomenon in which oligomeric protein binds to a ligand to change the conformation of the protein, resulting in a change in the biological activity of the protein.

Structure of protein that helps cancer cells

When cancer cells proliferate rapidly, they seem to need the help of a protein called survivin. According to reports by some researchers, survivin proteins are unexpectedly combined in pairs-this discovery is likely to provide a new mechanism for the design of anti-cancer drugs.

In order to find out exactly what role the survivin protein plays, Joseph Noel, a structural biologist in California, USA, and his colleagues took the lead in carefully observing its three-dimensional structure. They irradiated X-rays on the protein crystals and measured the deflection angle of the X-rays, which allowed the researchers to calculate the position of each atom in the protein. The results they obtained pointed out that survivin protein forms a kind of junction, which is not formed by other apoptosis inhibitors. These researchers reported in the July issue of "Nature Structural Biology" that a part of the survivin molecule unexpectedly joined with the corresponding part of another survivin molecule to form a dimer called a dimer. Protein pair. Researchers speculate that these dimers of survivin proteins may maintain key molecular structures during cell division. If this protein must be paired in order to function, then using a small molecule to separate them may be able to fight cancer.

Biochemist Guy Salvesen said that mastering the structure of the survivin protein "does not clarify the doubt about how it prevents cell suicide." But he said that the fact that these proteins pair up is really surprising, "It's almost hard to find unimportant dimerization regions." He also agreed that the interface between the two proteins would be a good target for anti-cancer drugs to focus on.

source

The main sources of protein are meat, eggs, milk, and legumes. Generally speaking, protein from animals is of high quality and contains sufficient essential amino acids. There are about 8 essential amino acids, which cannot be synthesized by the human body. They must be ingested from food. If there is insufficient stock of an essential amino acid in the body, sufficient protein cannot be synthesized for use by various tissues of the body, and other excess proteins will also be metabolized by the body. It’s wasted, so it’s important to ensure adequate intake of essential amino acids. Plant-based protein usually has insufficient content of 1-2 kinds of essential amino acids, so vegetarians need to consume a variety of foods and obtain enough essential amino acids from various combinations. A piece of cooked meat the size of a playing card contains about 30-35 grams of protein, a large cup of milk contains about 8-10 grams, and a half cup of various beans contains about 6-8 grams. So eating a piece of meat the size of a poker card, drinking two cups of milk, some beans, plus a small amount of vegetables, fruits, and rice, you can get about 60-70 grams of protein, which is enough for a long-distance runner weighing 60 kg. need. If your demand is relatively large, you can drink an extra glass of milk, or eat more meat, to get enough protein.