The regulator CdsS/CdsR two-component system modulates expression of genes involved in chitin degradation of Pseudoalter
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ORIGINAL PAPER
The regulator CdsS/CdsR two-component system modulates expression of genes involved in chitin degradation of Pseudoalteromonas piscicida strain O-7 Katsushiro Miyamoto · Mina Okunishi · Eiji Nukui · Takahiro Tsuchiya · Takeshi Kobayashi · Chiaki Imada · Hiroshi Tsujibo
Received: 28 February 2007 / Revised: 27 June 2007 / Accepted: 2 July 2007 / Published online: 19 July 2007 © Springer-Verlag 2007
Abstract Pseudoalteromonas piscicida strain O-7 (formerly Alteromonas sp. strain O-7) is an eYcient degrader of chitin in the marine environment. The chitinolytic system of the strain consists of many enzymes induced by Nacetylglucosamine (GlcNAc). This paper reports that CdsR, which is a response regulator of CdsS/CdsR two-component signal transduction system, is bound to near the promoter region of GlcNAc-induced aprIV gene. The CdsR protein as a response regulator was transphosphorylated by the CdsS protein as a sensor kinase. Furthermore, the transphosphorylation from CdsS to CdsR was promoted by chitin degradation products and a metabolite. The CdsR protein was also phosphorylated by acetyl phosphate which is an indicator of nutritive conditions of cells. Gel mobility shift assays demonstrated that phosphorylated CdsR (CdsR-P) was bound to not only near the promoter region of aprIV gene but also those of chiA, chiB, chiC, chiD and cbp1 genes which are induced in the presence of GlcNAc. Footprinting analysis demonstrated that CdsR-P was bound to the sequences around the transcriptional start sites of aprIV and chiD genes. These results indicate that CdsR is one of the common regulators of these genes involved in chitin degradation of the strain. Communicated by Pierre Béguin. K. Miyamoto · M. Okunishi · E. Nukui · T. Tsuchiya · H. Tsujibo (&) Department of Microbiology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan e-mail: [email protected] T. Kobayashi · C. Imada Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, Minato-ku, Tokyo 108-8477, Japan
Keywords Chitin · Degradation · Response regulator · Sensor · Chitinase · Protease · Marine · Alteromonas
Introduction Chitin, an insoluble linear -1,4-linked polymer of N-acetylglucosamine (GlcNAc), is the second most abundant organic compound found in nature. In the aquatic biosphere alone, it is estimated that more than 1011 metric tons of chitin are produced annually (Keyhani and Roseman 1999). This polysaccharide is a major component of the exoskeleton and endoskeleton of many marine organisms, such as Mollusca, Coelenterata, Protozoa and Crustacea (Jannatipur et al. 1987). Since carbon and nitrogen are generally limited in the marine environment, chitin is a particularly important nutrient source for marine organisms (Gooday 1990). Chitinolytic marine bacteria are the principal mediators of chitin degradation and play a crucial role in the recycling of chitinous materials (Yu et al. 1991). To degrade chitin, chitinolytic bacteria possess highly soph
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