Role and mechanism of the maturation cleavage of VP0 in poliovirus assembly: Structure of the empty capsid assembly intermediate at 2.9 Å resolution

Abstract

The crystal structure of the Pl/Mahoney poliovirus empty capsid has been determined at 2.9 A resolution. The empty capsids differ from mature virions in that they lack the viral RNA and have yet to undergo a stabilizing maturation cleavage of VPO to yield the mature capsid proteins VP4 and VP2. The outer surface and the bulk of the protein shell are very similar to those of the mature virion. The major differences between the 2 structures are focused in a network formed by the N-terminal extensions of the capsid proteins on the inner surface of the shell. In the empty capsids, the entire N-terminal extension of V P l , as well as portions corresponding to VP4 and the N-terminal extension of VP2, are disordered, and many stabilizing interactions that are present in the mature virion are missing. In the empty capsid, the VPO scissile bond is located some 20 A away from the positions in the mature virion of the termini generated by VPO cleavage. The scissile bond is located on the rim of a trefoilshaped depression in the inner surface of the shell that is highly reminiscent of an RNA binding site in bean pod mottle virus. The structure suggests plausible (and ultimately testable) models for the initiation of encapsidation, for the RNA-dependent autocatalytic cleavage of VPO, and for the role of the cleavage in establishing the ordered N-terminal network and in generating stable virions.Keywords: capsid proteins; empty capsid; encapsidation initiation; maturation cleavage; poliovirus; viral RNA; virion stability Poliovirus is a member of the picornavirus family. This family includes a large number of related small spherical viruses consisting entirely of a protein shell (approximately 300 A in diameter) and a single-stranded RNA genome (-7,500 nucleotides) of positive polarity. The family is subdivided into several genera, including the enteroviruses (polioviruses, coxsackieviruses,

Cleavage site analysis in picornaviral polyproteins: Discovering cellular targets by neural networks

“…I). Concomitantly with RNA encapsidation, VPO is cleaved to VP4 and VP2; it is believed that the RNA itself exerts a catalytic function in this event (Arnold et a!., 1987;Harber et al, 1991;Bishop &Anderson, 1993;Basavappa et al, 1994).…”

“…I). Concomitantly with RNA encapsidation, VPO is cleaved to VP4 and VP2; it is believed that the RNA itself exerts a catalytic function in this event (Arnold et a!., 1987;Harber et al, 1991;Bishop &Anderson, 1993;Basavappa et al, 1994).In addition to processing of the viral polyprotein, the proteinases also cleave cellular targets. When infected with poliovirus, at least nine acidic and five basic cellular proteins were shown to be degraded in two-dimensional gel electrophoresis (Urzanqui & Carrasco, 1989).…”

Crystal Structures of Enterovirus 71 (EV71) Recombinant Virus Particles Provide Insights into Vaccine Design

“…Although empty particles are not thought to be direct precursors of mature virions, they may function as reservoirs of capsid components (11)(12)(13). For poliovirus, empty particles are unstable, readily converting from D-type native antigenicity to a state with altered antigenic properties (C-type) (9,14,15). EV71 cultured for vaccine development produces both full virions and empty particles, and the content of empty particles is at least 2-fold more than the full virion in the final production yield (16).…”

Dissociation of an antiviral compound from the internal pocket of human rhinovirus 14 capsid

“…These changes are of particular interest in view of the inhibition of viral uncoating by WIN compounds. Cell attachment and uncoating to release viral RNA are associated with large conformational transitions in the capsid that transform the overall structure of the particle (25) and perturb interactions at the 5-fold axis (26,27). In addition to release of viral RNA, the N termini of VP1 and VP4 are externalized from their internal location in the capsid core.…”