Structural conservation of the myoviridae phage tail sheath protein fold.

Summary Bacteriophage phiKZ is a giant phage that infects Pseudomonas aeruginosa , a human pathogen. The phiKZ virion consists of a 1450 A diameter icosahedral head and a 2000 A-long contractile tail. The structure of the whole virus was previously reported, showing that its tail organization in the extended state is similar to the well-studied Myovirus bacteriophage T4 tail. The crystal structure of a tail sheath protein fragment of phiKZ was determined to 2.4 A resolution. Furthermore, crystal structures of two prophage tail sheath proteins were determined to 1.9 and 3.3 A resolution. Despite low sequence identity between these proteins, all of these structures have a similar fold. The crystal structure of the phiKZ tail sheath protein has been fitted into cryo-electron-microscopy reconstructions of the extended tail sheath and of a polysheath. The structural rearrangement of the phiKZ tail sheath contraction was found to be similar to that of phage T4.