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J. Biol. Chem., Vol. 281, Issue 19, 13083-13091, May 12, 2006

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The Critical Roles of Polyamines in Regulating ColE7 Production and Restricting ColE7 Uptake of the Colicin-producing Escherichia coli^*

Yi-Hsuan Pan, Chen-Chung Liao, Chou-Chiang Kuo, Kow-Jen Duan, Po-Huang Liang^¶, Hanna S. Yuan^||, Shiau-Ting Hu^**, and Kin-Fu Chak¹

From the Institute of Biochemistry and the ^**Institute of Microbiology and Immunology, National Yang Ming University, Taipei 11221, the Institute of Bioengineering, Tatung University, Taipei 10452, and the ^¶Institute of Biological Chemistry and ^||Molecular Biology, Academic Sinica, Taipei 1529, Taiwan

The ColE7 operon is an SOS response regulon, which encodes bacteriocin ColE7 to kill susceptible Escherichia coli and its related enterobacteria under conditions of stress. We have observed for the first time that polyamines confer limited resistance against ColE7 on E. coli cells. Thus, this study aims to investigate the role of polyamines in modulating the protective effect of the E. coli cells against colicin. In the experiments, we surprisingly found that endogenous polyamines are also essential for ColE7 production, and the rate of polyamine synthesis is directly related to the SOS response. Our experimental results further indicated that exogenous polyamines suppress the expression of TolA, BtuB, OmpF, and OmpC proteins that are responsible for ColE7 uptake. Moreover, two-dimensional gel electrophoresis revealed that the production of two periplasmic proteins, PotD and OppA, is increased in E. coli cells under ColE7 exposure. Based on these observations, we propose that endogenous polyamines may play a dual role in the ColE7 system. Polyamines may participate in initiating the expression of the SOS response of the ColE7 operon and simultaneously down-regulate proteins that are essential for colicin uptake, thus conferring a survival advantage on colicin-producing E. coli under stress conditions in the natural environment.

Received for publication, October 19, 2005 , and in revised form, February 27, 2006.

^* This work was supported by National Science Council of the Republic of China Research Grants NSC 93-2311-B-010-002, NSC 93-2321-B-010-007, and NSC 94-2311-B-010-016 (to K.-F. C.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: Institute of Biochemistry, National Yang Ming University, Taipei, Taiwan 11221, Republic of China. Tel.: 886-2-28267129; Fax: 886-2-28264843; E-mail: kfchak{at}ym.edu.tw.

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