title: pH-induced conformational change of the rotavirus VP4 spike: implications for cell entry and antibody neutralization.
abstract: The rotavirus spike protein, VP4, is a major determinant of infectivity and neutralization. Previously, we have shown that trypsin-enhanced infectivity of rotavirus involves a transformation of the VP4 spike from a flexible to a rigid bilobed structure. Here we show that at elevated pH the spike undergoes a drastic, irreversible conformational change and becomes stunted, with a pronounced trilobed appearance. These particles with altered spikes, at a normal pH of 7.5, despite the loss of infectivity and the ability to hemagglutinate, surprisingly exhibit sialic acid (SA)-independent cell binding in contrast to the SA-dependent cell binding exhibited by native virions. Remarkably, a neutralizing monoclonal antibody that remains bound to spikes throughout the pH changes (pH 7 to 11 and back to pH 7) completely prevents this conformational change, preserving the SA-dependent cell binding and hemagglutinating functions of the virion. A hypothesis that emerges from the present study is that high-pH treatment triggers a conformational change that mimics a post-SA-attachment step to expose an epitope recognized by a downstream receptor in the rotavirus cell entry process. This process involves sequential interactions with multiple receptors, and the mechanism by which the antibody neutralizes is by preventing this conformational change.
authors.affiliation: Verna and McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA.
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Pesavento
authors.forename: Sue E
authors.initials: SE
authors.lastname: Crawford
authors.forename: Ed
authors.initials: E
authors.lastname: Roberts
authors.forename: Mary K
authors.initials: MK
authors.lastname: Estes
authors.forename: B V Venkataram
authors.initials: BV
authors.lastname: Prasad
mesh_terms: D036022:Capsid Proteins / Q000737:chemistry* / Q000235:genetics*; D006385:Hemagglutination Inhibition Tests; D006386:Hemagglutination Tests; D006863:Hydrogen-Ion Concentration; D007091:Image Processing, Computer-Assisted; D008958:Models, Molecular; D009500:Neutralization Tests; D011487:Protein Conformation; D012401:Rotavirus / Q000235:genetics / Q000276:immunology / Q000502:physiology*
chemical_list: D036022:Capsid Proteins; C060339:VP4 protein, Rotavirus