University:
Liberty University
Course:
BIOM 500 | Introduction to Biomedical Sciences
Academic year:

2024
Views:

338

Pages:

5
Author:

Sheha A.

**Secondary Structure of Protein** * Twisting and folding of polypeptide chain result in secondary structure. * It helps to the folding of the polypeptide chain, formed by the interaction between amino acids which are relatively close in the primary structure of amino acid. **Different Secondary Structure are: α-helix, β-sheet, bends, loops or disordered regions.** Among the α-helix & β-sheet structure represent the ordered secondary structure that are frequently present in protein. Bends & loops or disordered regions represent the minor secondary structure. **α-Helix** * This is most common secondary structure found in proteins. * Ex: α-helix seen in hemoglobin, myoglobin, collagen etc. **Features** * α-helix is a right-handed coiled structure. * α-helix structure is stabilized by intra-peptide hydrogen bonding. Hydrogen bond formed b/w 5th peptide bond is hydrogen bonded by the peptide bond of 13th amino acid. **Ex:** * Each turn of helix contains 3.6 amino acid residues, and each amino acid is separated by a distance of 1.5 Å. * Proline / hydroxyproline and glycine are considered as helix destabilizing amino acids, as they disrupt the formation of α-helix producing the bend. * Amino acids alanine, cysteine promote the helix formation. **Hydrogen bond is formed between peptide bond** N-H C=O | H (hydrogen bond) N-H C=O COOH