Long Noncontractile Tail Machines of Bacteriophages
In this chapter, we describe the structure, assembly, function, and evolution of the long, noncontractile tail of the siphophages, which comprise ∼60% of the phages on earth. We place particular emphasis on features that are conserved among all siphophages, and trace evolutionary connections between these phages and myophages, which possess long contractile tails. The large number of high-resolution structures of tail proteins solved recently coupled to studies of tail-related complexes by electron microscopy have provided many new insights in this area. In addition, the availability of thousands of phage and prophage genome sequences has allowed the delineation of several large families of tail proteins that were previously unrecognized. We also summarize current knowledge pertaining to the mechanisms by which siphophage tails recognize the bacterial cell surface and mediate DNA injection through the cell envelope. We show that phages infecting Gram-positive and Gram-negative bacteria possess distinct families of proteins at their tail tips that are involved in this process. Finally, we speculate on the evolutionary advantages provided by long phage tails.
KeywordsHydrolysis Sucrose Carbohydrate Recombination Bacillus
The authors thank Christian Cambillau for supplying the image used in Fig. 6.7. We also thank Petr Leiman for his encouragement during the writing of this chapter and for reading the final version. Work in our labs is supported by operating grants from the Canadian Institutes of Health Research to A.R.D. (Fund No. MOP-77680) and to K.L.M. (Fund No. MOP-6279).
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