Protein overview

Protein is a complex organic compound, formerly known as "朊". The concept of protein was first proposed by the Swedish chemist Yongs Becherius in 1838, but at the time people did not understand the core role of proteins in the body. In 1926, James B. Sumner revealed that urease is a protein, and for the first time proved that the enzyme is a protein. The first antigenic peptide protein to be sequenced was insulin, which was completed by Frederick Sanger and he won the 1958 Nobel Prize in Chemistry. The first parsed protein structure, including the structure of hemoglobin and myoglobin, was X-ray crystallography; the work was done by Max Perutz and John Kendrew in 1958, and they were thus acquired in 1962. Nobel Prize in Chemistry.

structure:
Proteins are formed by linear alignment of amino acid molecules, and the carboxyl and amino groups of adjacent amino acid residues are linked together by peptide bonds. The amino acid sequence of a protein is encoded by the corresponding gene. In addition to the 20 "standard" amino acids encoded by the genetic code. In the antigenic peptide protein, certain amino acid residues can also be post-translationally modified to undergo chemical structural changes to activate or regulate the protein. Multiple proteins can work together, often by combining them to form a stable protein complex that performs a specific function.
All amino acids share common structural characteristics, including the alpha carbon atom attached to the amino group, a carboxyl group, and different side chains attached to the alpha carbon atom. However, proline differs from this basic structure in that it contains a special cyclic structure in which a side chain is bonded to an amino group such that its amino group has a relatively fixed conformation in the peptide bond. .
The side chains of standard amino acids are important elements that make up the structure of proteins. They have different chemical properties and are therefore essential for the function of proteins.
The amino acids in the polypeptide chain are linked to each other by a peptide bond formed by a dehydration reaction; once the peptide bond is formed as part of the protein, the amino acid is called a "residue" and the carbon, nitrogen, and oxygen atoms attached to the chain are attached. Known as the "main chain" or "protein skeleton." Since the peptide bond has two resonance states and has a certain double bond characteristic, a peptide plane is formed between adjacent α carbons; and the dihedral angle on both sides of the peptide bond determines the local morphology of the protein skeleton.
Due to the asymmetry of amino acids (amino and carboxyl groups at each end), the protein chains are directional. The starting end of the protein chain has a free amino group, called the N-terminus or the amino terminus; the tail has a free carboxyl group, called the C-terminus or the carboxy-terminus.
Features:
Like other biomacromolecules (such as polysaccharides and nucleic acids), proteins are an essential component of living organisms on Earth and participate in every process of cellular life. Enzymes are the most common class of proteins that catalyze biochemical reactions, especially for the metabolism of organisms. In addition to enzymes, there are many structural or mechanical proteins, such as actin and myosin in muscle, and tubulin in the cytoskeleton (participating in the formation of intracellular support networks to maintain cell shape). Other antigenic peptide proteins are involved in cell signaling, immune response, cell adhesion, and cell cycle regulation. At the same time, protein is also an essential nutrient in people's daily diet. This is because the animal itself cannot synthesize all essential amino acids. By digesting the protein food (degrading the protein into amino acids), the human body can use the absorbed amino acid for itself. Protein synthesis.

other:
The meanings of the terms "protein", "polypeptide" and "peptide" overlap to some extent and are often confusing. "Protein" generally refers to a molecule that has intact biological functions and has a stable structure; while "peptide" generally refers to a shorter stretch of amino acids, often without a stable three-dimensional structure. However, the line between "protein" and "peptide" is very vague, usually bounded by 20-30 residues. "Polypeptide" can refer to a linear single-stranded molecule of amino acids of any length, but often indicates the absence of a stable tertiary structure.

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