Structure and genetic analysis of the arterivirus nonstructural protein 7 alpha

Abstract

Arterivirus replicase polyproteins are cleaved into at least 13 mature nonstructural proteins (nsps), and in particular the nsp5-to-nsp8 region is subject to a complex processing cascade. The function of the largest subunit from this region, nsp7, which is further cleaved into nsp7 alpha and nsp7 beta, is unknown. Using nuclear magnetic resonance (NMR) spectroscopy, we determined the solution structure of nsp7 alpha of equine arteritis virus, revealing an interesting unique fold for this protein but thereby providing little clue to its possible functions. Nevertheless, structure-based reverse genetics studies established the importance of nsp7/nsp7 alpha for viral RNA synthesis, thus providing a basis for future studies.