What is the secondary structure of protein?

Protein is a basic building block of living things. Almost all living things contain large amounts of protein because protein can be converted into fat or energy, providing the body with a steady supply of nutrients. Protein is not a simple substance, its composition is also very complex. For example, protein is divided into several levels of structure. Let's take a look at what the secondary structure of protein is.

Protein structure refers to the spatial structure of protein molecules. Proteins are mainly composed of chemical elements such as carbon, hydrogen, oxygen, and nitrogen. They are an important type of biological macromolecules. All proteins are polymers formed by the connection of 20 different amino acids. After forming proteins, these amino acids are called residues.

The secondary structure of a protein refers to the regularly repeated conformations in its polypeptide chain, which is limited to the local spatial arrangement of the main chain atoms and does not include the relationships with other segments of the peptide chain and the side chain conformations. The secondary structures mainly include α-helix, β-sheet and β-turn. Common secondary structures include α-helix and β-sheet. The secondary structure is maintained by hydrogen bonds formed between the carbonyl and amide groups on the backbone, which are the main force stabilizing the secondary structure.

When a protein forms a three-dimensional structure, its polypeptide chain first folds into an α-helix.

Helix and β-sheet structures, and can be further folded into a spherical shape. At this time, the α-helix and β-type structures are called secondary structures. Outside of proteins, for example, tRNA has a cloverleaf structure, which can also be called a secondary structure.

Primary structure: the linear sequence of amino acids that makes up the protein polypeptide chain.

Secondary structure: A stable structure formed by hydrogen bonds between C=O and NH groups of different amino acids, mainly α-helix and β-fold.

Tertiary structure: The three-dimensional structure of a protein molecule formed by the arrangement of multiple secondary structure elements in three-dimensional space.

Quaternary structure: used to describe functional protein complex molecules formed by interactions between different polypeptide chains (subunits).

In addition to these structural hierarchies, proteins can switch between multiple similar structures to perform their biological functions. For functional structural changes, these tertiary or quaternary structures are often described in terms of chemical conformations, and the corresponding structural transformations are called conformational changes.

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