Domain 2 of Nonstructural Protein 5A(NS5A)of Hepatitis C Virus Is Natively Unfolded

摘要

Nonstructural protein 5A protein(NS5A)of hepatitis C virus(HCV)plays an important role in the regulation of viral replication,interferon resistance,and apoptosis.HCV NS5A comprises three domains.Recently the structure of domain 1 has been determined,revealing a structural scaffold with a novel zinc-binding motif and a disulfide bond.At present,the structures of domains 2 and 3 remain undefined.Domain 2 of HCV NS5A(NS5A-D2)is important for functions of NS5A and involved in molecular interactions with its own NS5B and PKR,a cellular interferon-inducible serine/threonine specific protein kinase.In this study we performed structural analysis of domain 2 by multinuclear nuclear magnetic resonance(NMR)spectroscopy.The analysis of the backbone ~1H,~(13)C,and ~(15)N resonances,~3J_(HN alpha)coupling constants,and 3D NOE data indicates that NS5A-D2 lacks secondary structural elements and reveals characteristics of unfolded proteins.NMR relaxation parameters confirmed the lack of rigid structure in the domain.The absence of an ordered conformation and the observation of a highly dynamic behavior of NS5A-D2 may provide an underlying molecular basis on its physiological function to allow NS5A-D2 to interact with a variety of biological partners.