Complementarity in the Supramolecular Design of Arenaviruses and Retroviruses Revealed by Electron Cryomicroscopy and Image Analysis (original) (raw)

Arenaviruses are rodent-borne agents of diseases, including potentially lethal human hemorrhagic fevers. These enveloped viruses encapsidate a bisegmented ambisense single-stranded RNA genome that can be packaged in variable copy number. Electron cryomicroscopy and image analysis of New World Pichinde and Tacaribe arenaviruses and Old World lymphocytic choriomeningitis virus revealed pleomorphic enveloped particles ranging in diameter from ϳ400 to ϳ2,000 Å. The surface spikes were spaced ϳ100 Å apart and extended ϳ90 Å from the maximum phospholipid headgroup density of the outer bilayer leaflet. Distinctive stalk and head regions extended radially ϳ30 and ϳ60 Å from the outer bilayer leaflet, respectively. Two interior layers of density apposed to the inner leaflet of the viral lipid bilayer were assigned as protein Z and nucleoprotein (NP) molecules on the basis of their appearance, spacing, and projected volume. Analysis of en face views of virions lacking the GP-C spikes showed reflections consistent with paracrystalline packing of the NP molecules in a lattice with edges of ϳ57 and ϳ74 Å. The structural proteins of retroviruses and arenaviruses assemble with similar radial density distributions, using common cellular components.