Bacteriophage PM2 has a protein capsid surrounding a spherical proteinaceous lipid core

The marine double-stranded DNA (dsDNA) bacteriophage PM2, studied since 1968, is the type organism of the family Corticoviridae, infecting two gram-negative Pseudoalteromonas species. The virion contains a membrane underneath an icosahedral protein capsid composed of two structural proteins. The purified major capsid protein, P2, appears as a trimer, and the receptor binding protein, P1, appears as a monomer. The C-terminal part of P1 is distal and is responsible for receptor binding activity. The rest of the structural proteins are associated with the internal phospholipid membrane enclosing the viral genome. This internal particle is designated the lipid core. The overall structural organization of phage PM2 resembles that of dsDNA bacteriophage PRD1, the type organism of the family Tectiviridae.