protein molecular structure

Biochemistry, Human Health Ninth Edition, these four levels of structure together constitute the complex molecular structure of proteins, enabling them to perform various biological functions.

Edited at 2024-02-08 16:32:57

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protein molecular structure

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Outline

protein molecular structure

primary structure

The sequence of amino acids in a protein molecule from the N-terminus to the C-terminus is called the primary structure of the protein.

Primary structure is the basis of protein spatial conformation and specific biological functions, but primary structure is not the only factor that determines protein spatial conformation.

The main chemical bonds in the primary structure: peptide bonds, and some proteins also include disulfide bonds

secondary structure

The local spatial structure of a certain peptide chain in a protein molecule, that is, the relative spatial position of the backbone atoms of the peptide chain, and does not involve the side chain conformation of the amino acid residues.

The relative spatial position of two adjacent peptide units is determined by the free rotation angle of the two single bonds connected to the α carbon atom on the peptide unit.

alpha-helix

Right-handed helix, amino acid side chains extend outside the helix Every 3.6 amino acid residues helix rises once, the helix pitch is 0.54nm, and the helix diameter is 0.5nm. Relying on hydrogen bonds to maintain the helix, the direction of the hydrogen bonds is parallel to the long axis of the helix Often have bisexual characteristics and are scalable (elastic)

β-sheet

Each peptide unit is sequentially folded into a zigzag shape with alpha carbon atoms. The side chains are alternately located above and below the zigzag structure. The zigzag structures within a peptide chain are arranged in parallel and can run in the same direction or in opposite directions.

β-turn

Often occurs at corners where the peptide chain undergoes a 180° turn Usually consists of 4 amino acid residues The second residue is often proline

Ω-ring

They often appear on the surface of protein molecules, mainly hydrophilic residues, and play an important role in molecular recognition.

random curl

Commonly found in proteins

Side chains affect the formation of secondary structure

charge

size

Rigid five-membered ring of proline

structural motif

Structural motifs can be composed of 2 or more peptide segments and are structural components with specific spatial conformations and specific functions in protein molecules (functional super-secondary structures)

tertiary structure

It refers to the relative spatial position of all amino acid residues in the entire peptide chain, that is, the arrangement position of all atoms in the entire peptide chain in three-dimensional space.

Tertiary structure is the highest order structure that a protein of a peptide chain can form.

domain

Proteins with larger molecular weights are often folded into multiple regions with a relatively compact and stable structure, each of which performs its own function, called a domain.

The sum of domain functions ≠ protein function

Chaperone

The polypeptide chain of a protein needs to be folded into the correct spatial conformation to have biological functions, which cannot be achieved without the help of molecular chaperones

Quaternary structure

The spatial arrangement of each subunit in a protein molecule and the layout and interaction of subunit contact sites are called the quaternary structure of the protein.

A polypeptide chain with a complete tertiary structure, called a subunit