Members of this family of viral domains adopt a structure consisting of a single-stranded right-handed beta-helix, which in turn is made of parallel beta-strands and short turns. They are required for recognition of the 0-antigenic repeating units of the cell surface, and for subsequent infection of the bacterial cell [1].

1: Crystal structure of phage P22 tailspike protein complexed with Salmonella sp. O-antigen receptors. Steinbacher S, Baxa U, Miller S, Weintraub A, Seckler R, Huber R; Proc Natl Acad Sci U S A. 1996;93:10584-10588. PMID:8855221