Bacteriophage P22 tailspike protein

In the first edition of this book this chapter was entitled "Antiparallel Beta Structures" but we have had to change this because an entirely unexpected structure, the p helix, was discovered in 1993. The p helix, which is not related to the numerous antiparallel p structures discussed so far, was first seen in the bacterial enzyme pectate lyase, the stmcture of which was determined by the group of Frances Jurnak at the University of California, Riverside. Subsequently several other protein structures have been found to contain p helices, including extracellular bacterial proteinases and the bacteriophage P22 tailspike protein. 

A more complex p helix is present in pectate lyase and the bacteriophage P22 tailspike protein. In these p helices each turn of the helix contains three short p strands, each with three to five residues, connected by loop regions. The p helix therefore comprises three parallel p sheets roughly arranged as the three sides of a prism. However, the cross-section of the p helix is not quite triangular because of the arrangement of the p sheets. Two of the sheets are... 

The number of helical turns in these structures is larger than those found so far in two-sheet p helices. The pectate lyase p helix consists of seven complete turns and is 34 A long and 17-27 A in diameter (Figure 5.30) while the p-helix part of the bacteriophage P22 tailspike protein has 13 complete turns. Both these proteins have other stmctural elements in addition to the P-helix moiety. The complete tailspike protein contains three intertwined, identical subunits each with the three-sheet p helix and is about 200 A long and 60 A wide. Six of these trimers are attached to each phage at the base of the icosahedral capsid. 

Figure 2-17 Wire model of the tailspike protein of bacteriophage P22 of Salmonella. Three of these fishshaped molecules associate as a trimer to form the spike. From Steinbacher et al.123...

Carbonell X, Villaverde A, Peptide display on functional tailspike protein of bacteriophage P22, Gene, 176 225-229, 1996. 

The tailspike protein from bacteriophage P22 is well suited for the second approach. The tailspike is a structural protein of P22. It is the last protein to bind to virus capsids during morphogenesis. The tailspike is also an endorhamnosidase which cleaves the 0-antigen protruding from its host cell Salmonella upon... 

Other bacteriophages have been tested for polypeptide display. The minor fibrous protein fibritin of phage T4 has been fused at the C-terminus with a polypeptide of 53 residues [7]. An antigenic peptide has been fused to the C-terminus of the tailspike protein of Salmonella typhimurium P22 bacteriophage [8]. 

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