REGULAR ARTICLES

Cell Research (2004); 14(3): 208-216

Characterization of a novel toxin-antitoxin module, VapBC, encoded by Leptospira interrogans chromosome

Yi Xuan ZHANG^{1, 2}, Xiao Kui GUO³, Chuan WU², Bo BI¹, Shuang Xi REN⁴, Chun Fu WU¹, Guo Ping ZHAO^{2, 4}

¹Pharmaceutical Department, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016,China.
²Research Center of Biotechnology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 500 Caobao Road, Shanghai 200233, China.
³Department of Microbiology and Parasitology, Shanghai Second Medical University, 280 Chongqingnan Road, Shanghai 200025, China.
⁴Chinese National Human Genome Center at Shanghai (CHGCS), 250 Bibo Road, ZhangJiang High Tech Park, Shanghai, 201203, China.

Received, Oct 21, 2003     Revised, Apr 25, 2004     Accepted, Apr 28, 2004

Correspondence: Guo Ping ZHAO +86-21-50801919 (phone) +86-21-50801922 (fax) gpzhao@sibs.ac.cn

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Abstract

Comparative genomic analysis of the coding sequences (CDSs) of Leptospira interrogans revealed a pair of closely linked genes homologous to the vapBC loci of many other bacteria with respect to both deduced amino acid sequences and operon organizations. Expression of single vapC gene in Escherichia coli resulted in inhibition of bacterial growth, whereas co-expression of vapBC restored the growth effectively. This phenotype is typical for three other characterized toxin-antitoxin systems of bacteria, i.e., mazEF[1], relBE[2] and chpIK[3]. The VapC proteins of bacteria and a thermophilic archeae, Solfolobus tokodaii, form a structurally distinguished group of toxin different from the other known toxins of bacteria. Phylogenetic analysis of both toxins and antitoxins of all categories indicated that although toxins were evolved from divergent sources and may or may not follow their speciation paths (as indicated by their 16s RNA sequences), co-evolution with their antitoxins was obvious.

Keywords: Leptospria, toxin-antitoxin system, VapBC, co-evolution, speciation.