VP1

VP1 commonly refers to a structural protein of picornaviruses, notably poliovirus and related enteroviruses and rhinoviruses. It is one of the four capsid proteins, VP1 through VP4, encoded in the P1 region of the viral polyprotein. After translation, the polyprotein is processed by viral proteases to produce mature capsid proteins; in many viruses VP0 is further cleaved into VP2 and VP4, while VP1 remains separate on the virion surface.

VP1 is a relatively large external capsid protein that, together with VP2 and VP3, forms the outer shell of the icosahedral virion. The N-terminus of VP1 is exposed on the virion surface and, along with flexible surface loops, contributes to receptor binding and antigenicity. The so-called canyon region in VP1 is a key site for receptor interaction in several picornaviruses, influencing entry into host cells. VP1 also contains major neutralization epitopes that are targets for the host immune response.

Genetic variation in VP1 underpins serotype diversity among picornaviruses. Sequencing of the VP1 gene is commonly used for typing and phylogenetic analysis, and to trace transmission during outbreaks, including poliovirus molecular epidemiology.

In research, VP1 structure has been resolved by X-ray crystallography and cryo-electron microscopy, contributing to understanding of capsid assembly and antigenic variation. VP1 is not functional alone; it is part of the assembled virion.