X-ray Crystallographic Structure of the Norwalk Virus Capsid

TLDR

Norwalk virus, a non‑cultivatable human calicivirus, is the major cause of epidemic gastroenteritis in humans. The first X‑ray structure of a Norwalk virus capsid, composed of 180 copies of a single protein, reveals a protruding P domain linked by a flexible hinge to a shell domain with an eight‑stranded β‑sandwich, and a unique P‑domain subdomain resembling EF‑Tu that likely determines strain specificity and cell binding.

Abstract

Norwalk virus, a noncultivatable human calicivirus, is the major cause of epidemic gastroenteritis in humans. The first x-ray structure of a calicivirus capsid, which consists of 180 copies of a single protein, has been determined by phase extension from a low-resolution electron microscopy structure. The capsid protein has a protruding (P) domain connected by a flexible hinge to a shell (S) domain that has a classical eight-stranded β-sandwich motif. The structure of the P domain is unlike that of any other viral protein with a subdomain exhibiting a fold similar to that of the second domain in the eukaryotic translation elongation factor–Tu. This subdomain, located at the exterior of the capsid, has the largest sequence variation among Norwalk-like human caliciviruses and is likely to contain the determinants of strain specificity and cell binding.