Novel Inter-Subunit Contacts in Barley Stripe Mosaic Virus Revealed by Cryo-Electron Microscopy

Barley stripe mosaic virus (BSMV, genus Hordeivirus) is a rod-shaped single-stranded RNA virus similar to viruses of the structurally characterized and well-studied genus Tobamovirus. Here we report the first high-resolution structure of BSMV at 4.1 Å obtained by cryo-electron microscopy. We discovered that BSMV forms two types of virion that differ in the number of coat protein (CP) subunits per turn and interactions between the CP subunits. While BSMV and tobacco mosaic virus CP subunits have a similar fold and interact with RNA using conserved residues, the axial contacts between the CP of these two viral groups are considerably different. BSMV CP subunits lack substantial axial contacts and are held together by a previously unobserved lateral contact formed at the virion surface via an interacting loop, which protrudes from the CP hydrophobic core to the adjacent CP subunit. These data provide an insight into diversity in structural organization of helical viruses. [Display omitted] •Determined the near-atomic structure of barley stripe mosaic virus (BSMV)•Two forms of BSMV were found, both of which are important for its life cycle•Identified a new lateral contact that is essential for the stability of BSMV•BSMV structure may offer an alternative to TMV in biotemplated materials Clare et al. have determined the structure of barley stripe mosaic virus at 4.1 Å and found that there were two distinct virions. The authors have found a new lateral contact between the capsid proteins that is essential for virion stability.