Tunnels modulate ligand flux in a heme nitric oxide/ oxygen binding (H-NOX) domain

摘要

Proteins have evolved a variety of structures that provide the basis for specific biological functions. For example, enzymes (proteins that catalyze biochemical reactions) possess pockets and channels that mediate the entry and binding of reactants, sequester reaction intermediates, and facilitate the exit of reaction products. Protein function can be extended and diversified with the support of small, tightly bound molecules known as cofactors. Proteins that bind an iron-containing cofactor called heme (commonly referred to as hemoproteins or heme proteins) are found in organisms from bacteria to humans. The structural features of heme proteins work in concert with the heme cofactor to tune heme chemistry for various functions (e.g., electron transfer, catalysis, and diatomic gas binding) (1).