Members of this family of viral baseplate structural proteins adopt a structure consisting of a three-layer beta-sandwich with two finger-like loops containing an alpha-helix at the opposite sides of the sandwich. The two peripheral, five-stranded, antiparallel beta-sheets are stacked against the middle, four-stranded, antiparallel beta-sheet. Attachment of this family of proteins to the baseplate during assembly creates a binding site for subsequent attachment of Gp6 [1].

1: Structure and location of gene product 8 in the bacteriophage T4 baseplate. Leiman PG, Shneider MM, Kostyuchenko VA, Chipman PR, Mesyanzhinov VV, Rossmann MG; J Mol Biol. 2003;328:821-833. PMID:12729757