This protein family includes Gp22 from Bacillus phage SPP1 (Swiss:O48465), an protein that shows a significant structural similarity with the N-terminal shoulder domain (Pfam:PF20747) of Receptor binding protein from Lactococcus phage p2 (RBP). It folds into two small three-stranded antiparallel beta-sheets and one large five-stranded mixed beta-sheet forming a pseudo-beta-sandwich [1].

1: Crystal structure of Bacillus subtilis SPP1 phage gp22 shares fold similarity with a domain of lactococcal phage p2 RBP. Veesler D, Blangy S, Spinelli S, Tavares P, Campanacci V, Cambillau C; Protein Sci. 2010;19:1439-1443. PMID:20506290