Viral membrane protein P3 assemblies into dimers. Each P3 subunit comprise a core of two perpendicular alpha helices, and subunits are bound together by a parallel two-stranded beta sheet. 120 asymmetric dimers form a layer below the outer capsid shell in an almost planar structure. This protein family is found in Bacteriophage PM2 and similar PRD1-adenovirus [1].

1: Insights into virus evolution and membrane biogenesis from the structure of the marine lipid-containing bacteriophage PM2. Abrescia NG, Grimes JM, Kivela HM, Assenberg R, Sutton GC, Butcher SJ, Bamford JK, Bamford DH, Stuart DI; Mol Cell. 2008;31:749-761. PMID:18775333