310 helix

310 helix is a type of secondary structure found in proteins and polypeptides. It is one of the several helical structures that proteins can fold into, the others being the more common alpha helix and the less common pi helix. The 310 helix is characterized by its tight turns and the presence of three amino acid residues per turn, with a hydrogen bond occurring between the carbonyl oxygen of the first amino acid and the amide hydrogen of the fourth. This structure is denoted as 3₁₀ because there are three amino acids per turn and the hydrogen bond occurs between the first and the tenth atom along the backbone.

Structure and Properties

The 310 helix has a rise per residue of approximately 2.0 Å and a pitch (the length of one complete turn along the helix axis) of approximately 6.0 Å, which is shorter than that of the alpha helix. This compact structure results from its tighter turns and the closer proximity of its hydrogen bonds. The phi (φ) and psi (ψ) angles of the amino acids in a 310 helix typically fall within a distinct range that differentiates it from other helical structures.

Occurrence

310 helices are less common than alpha helices in protein structures but are often found at the termini of alpha helices or in short stretches where they may serve as transitions between other secondary structures. Their presence can be critical for the function of some proteins, influencing their stability, folding, and interactions with other molecules.

Function

The specific role of 310 helices in proteins can vary widely depending on the context within which they are found. They may contribute to the stability of the protein, facilitate the binding of ligands, or participate in the protein's dynamic functions. Due to their potential to form quickly and with fewer residues, 310 helices might also play a role in the early stages of protein folding.

Detection and Analysis

The identification of 310 helices within protein structures is typically performed through X-ray crystallography or nuclear magnetic resonance (NMR) spectroscopy, followed by analysis using computational tools and databases that classify protein secondary structures.

Biological Significance

Understanding the presence and function of 310 helices within proteins is crucial for insights into protein structure-function relationships, the design of protein-based drugs, and the engineering of novel proteins with desired functions.