Curvature of the retroviral capsid assembly is modulated by a molecular switch

Abstract

AbstractDuring the maturation step, the capsid proteins (CAs) of a retrovirus assemble into polymorphic capsids, whose acute curvature is largely determined by insertion of 12 pentamers into the hexameric lattice. Despite years of intensive research, it remains elusive how the CA switches its conformation between the quasi-equivalent pentameric and hexameric assemblies to generate the acute curvature in the capsid. Here we report the high-resolution structural model of the RSV CA T=1 capsid. By comparing with our prior model of the RSV CA tubular assembly consisting entirely of hexameric lattices, we identify that a dozen of residues are the key to dictate the incorporation of acute curvatures in the capsid assembly. They undergo large torsion angle changes, which result a 34° rotation of the C-terminal domain relative to its N-terminal domain around the flexible interdomain linker, without substantial changes of either the conformation of individual domains or the assembly contact interfaces.