Question

What is the \(\alpha\) -helical structure in proteins?

Short answer

The α-helical structure in proteins is a right-handed coiled or spiral configuration of amino acids stabilized by hydrogen bonds. It is a common structural element in proteins, contributing to protein stability, flexibility, and functionality.

Step-by-step solution

Definition

The alpha helix (α-helix) is one of the primary ways that proteins can form their three-dimensional structure. It is a right-handed coiled or spiral configuration, in which all the backbone N-H groups (donor) of amino acids are hydrogen bonded to the backbone C=O groups of the amino acid situated three or four residues earlier along the protein sequence (acceptor).

Characteristics

A protein's alpha-helical structure has several defining characteristics. Each turn of the helix involves 3.6 amino acid residues, with an axial rise per residue of 1.5Å and a pitch (length of one complete turn along the helix axis) of 5.4Å. The alpha-helical structure is stabilized by hydrogen bonds. These bonds form between the hydrogen of the -NH group of an amino acid and the oxygen of the carbonyl group of another amino acid, typically four residues away.

Role in Proteins

The alpha helix is a vital structural component in a vast array of proteins. The alpha helix structures can vary in length and they play a crucial role in establishing the characteristics and functionality of the proteins. For example, they are prevalent in haemoglobin and keratin. The functionality of the protein, its stability, flexibility and the dynamics of the protein are determined by the alpha-helical content in the protein structure.