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The newly characterized colicin Y provides evidence of positive selection in pore-former colicin diversification

Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06511, USA¹
The Institute for Genomic Research, 9712 Medical Center Dr., Manassas, VA 20850, USA²
Dept of Human Genetics³ and Dept of Microbiology and Immunology⁴, University of Michigan, Ann Arbor, MI 48109, USA

Author for correspondence: David Friedman. Tel: +1 734 763 3142. Fax: +1 734 764 3562. e-mail: davidfri{at}umich.edu

Two evolutionary mechanisms have been proposed in the process of protein diversification of the large family of antimicrobial toxins of Escherichia coli, known as the colicins. Data from previous studies suggest that the relatively rare nuclease colicins appear to diversify primarily through the action of positive selection, whilst the more abundant pore-former colicins appear to diversify through the action of recombination. The complete DNA sequence of the newly characterized colicin plasmid, pCol-Let, isolated from a Yanomama Indian of South America, is presented here. This plasmid encodes a newly identified pore-former colicin, colicin Y. DNA and protein sequence comparisons of the colicin Y gene cluster and the encoded proteins with those of published pore-former colicins provide the first evidence that positive selection may also act to increase pore-former colicin diversity.

Keywords: colicins, positive selection, evolution, plasmid, Yanomama Indians

During the time this manuscript was being prepared for publication, our colleague James V. Neel passed away. The other authors wish to dedicate this work to his memory.

The GenBank accession number for the sequence reported in this paper is AF197335.

^b Present address: Viropharma Incorporated, 405 Eagleview Blvd, Exton, PA 19341, USA.

^c Present address: Washington University Medical School, Molecular Biology, Campus Box 8230, St Louis, MO 62110, USA.

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