Folding and conformational diversity of the NS1 protein from HRSV

ESTEBAN PRETEL; GABRIELA CAMPOREALE; GONZALO DE PRAT GAY

Granada

Congreso; 15th International Negative Strand Virus Meeting; 2013

Human respiratory syncytial virus (hRSV) is the most important infectious agent responsible for pediatric respiratory disease worldwide. The virus encodes two non-structural proteins, NS1 and NS2 that are unique to RSV. These proteins are known to suppress type I interferon (IFN) response and signalling, and to interact with members of different pathways. Although NS1 is considered one of the main virulence factors of hRSV, the biochemical and biophysical knowledge is very scarce and there is no structure available. In this work, we describe a comprehensive analysis of the NS1 protein stability, folding, and conformational equilibria. Despite being a monomer, an important portion of the molecule is subjected to slow conformational motions as judged from NMR experiments. Under different conditions NS1 is able to self-oligomerize. Mild temperatures induce conformational changes displaying a highly cooperative transition. As a result, soluble spherical oligomers (SOs) with amyloid-like or repetitive ß-sheet type of structures were found. Conformational stability analysed by chemical perturbation showed a cooperative unfolding of the monomeric protein in a fully reversible process. In the case of NS1SOs, two transitions were observed indicating the presence of a native-like monomeric intermediate prior to unfolding. Different solvent perturbations were remarkably coincident in the formation of ß-sheet enriched oligomer species with a secondary structure highly similar to those obtained alfer mild temperature treatment. Conformational complexity may well be related to NS1 function and binding promiscuity, expanding the possibilities of interactions in the different environments of the host cell.