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J. Bacteriol. doi:10.1128/JB.00095-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

ORF334 in Vibrio phage KVP40 plays the role of gp27 in T4 phage to form a hetero-hexameric complex

Department of Biomolecular Engineering, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4359-B39 Nagatsuta-cho, Midori-ku, Yokohama 226-8501 JAPAN; National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Central 2, Umezono 1-1-4, Tsukuba Science City Ibaraki 305-8568 JAPAN

^* To whom correspondence should be addressed. Email: farisaka{at}bio.titech.ac.jp.

	Abstract

KVP40 is a T4-related phage composed of 386 ORFs that has a broad host range. Here we have over-expressed, purified and biophysically characterized two of the proteins encoded in the KVP40 genome, namely gp5 and ORF334. Homology based comparison between KVP40 and its better characterized sister phage T4 was used to estimate the two KVP40 proteins function. KVP40 gp5 shared significant homology with T4 gp5 in the N and C terminal domain. Unlike T4 gp5, KVP40 gp5 lacked the internal lysozyme domain. Like T4 gp5, KVP40 gp5 was found to form a homo-trimer in solution. In stark contrast KVP40 ORF334 shared no significant homology with any known proteins from T4-related phages. KVP40 ORF334 was found to form a hetero-hexamer with KVP40 gp5 in solution in a near identical fashion to the interaction between T4 gp5 and gp27 proteins. Electron microscope image analysis of the KVP40 gp5-ORF334 complex indicated that it had very similar dimensions to the T4 gp5-gp27 structure. On the basis of our biophysical characterization along with positional genome information we propose that ORF334 is the ortholog of T4 gp27 and that it plays the role of linker between gp5 and the phage baseplate.