InterPro domain: IPR012332

The tailspike protein of Salmonella bacteriophage P22 is a viral adhesion protein that mediates attachment of the viral protein to host cell-surface lipopolysaccharide. The tailspike protein displays both receptor binding and destroying properties, inactivating the receptor by endoglycosidase activity. P22 tailspike is a homotrimer composed of 666 amino acid polypeptide chains. P22 tailspike consists of three main structural elements: the head-binding domain at the N terminus, the beta-helix in the centre of the protein, and the beta-prism and caudal fin at the C terminus [ 1 ]. The P22 tailspike protein contains similar structural elements to pectin lyase [ 2 ]. The binding of the disaccharide product occurs within a positively charged cleft formed by loops extending from the surface of the beta-helix structure. Amino acid residues responsible for recognition of the disaccharide, as well as potential catalytic residues, have been identified [ 3 ].

This superfamily represents the C-terminal domain of phage P22 tailspike proteins and includes proteins that display a similar pectin-lyase-type beta-helix fold.

1. C-terminal hydrophobic interactions play a critical role in oligomeric assembly of the P22 tailspike trimer. Protein Sci. 12, 2732-47
2. Crystal structure of chondroitinase B from Flavobacterium heparinum and its complex with a disaccharide product at 1.7 A resolution. J. Mol. Biol. 294, 1257-69
3. Biochemical characterization of the chondroitinase B active site. J. Biol. Chem. 277, 31179-86