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Publication Abstract from PubMed

Siphoviridae is the most abundant viral family on earth which infects bacteria as well as archaea. All known siphophages infecting gram+ Lactococcus lactis possess a baseplate at the tip of their tail involved in host recognition and attachment. Here, we report analysis of the p2 phage baseplate structure by X-ray crystallography and electron microscopy and propose a mechanism for the baseplate activation during attachment to the host cell. This approximately 1 MDa, Escherichia coli-expressed baseplate is composed of three protein species, including six trimers of the receptor-binding protein (RBP). RBPs host-recognition domains point upwards, towards the capsid, in agreement with the electron-microscopy map of the free virion. In the presence of Ca(2+), a cation mandatory for infection, the RBPs rotated 200 degrees downwards, presenting their binding sites to the host, and a channel opens at the bottom of the baseplate for DNA passage. These conformational changes reveal a novel siphophage activation and host-recognition mechanism leading ultimately to DNA ejection.

Structure of lactococcal phage p2 baseplate and its mechanism of activation.,Sciara G, Bebeacua C, Bron P, Tremblay D, Ortiz-Lombardia M, Lichiere J, van Heel M, Campanacci V, Moineau S, Cambillau C Proc Natl Acad Sci U S A. 2010 Mar 29. PMID:20351260^[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.