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Journal of Bacteriology, May 2002, p. 2360-2369, Vol. 184, No. 9
0021-9193/02/$04.00+0     DOI: 10.1128/JB.184.9.2360-2369.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Critical Regions of secM That Control Its Translation and Secretion and Promote Secretion-Specific secA Regulation

Shameema Sarker and Donald Oliver*

Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut 06459

Received 25 September 2001/ Accepted 28 January 2002

SecA is an essential ATP-driven motor protein that binds to presecretory or membrane proteins and the translocon and promotes the translocation or membrane integration of these proteins. secA is subject to a protein secretion-specific form of regulation, whereby its translation is elevated during secretion-limiting conditions. A novel mechanism that promotes this regulation involves translational pausing within the gene upstream of secA, secM. The secM translational pause prevents formation of an RNA helix that normally blocks secA translational initiation. The duration of this pause is controlled by the rate of secretion of nascent SecM, which in turn depends on its signal peptide and a functional translocon. We characterized the atypical secM signal peptide and found that mutations within the amino-terminal region specifically affect the secM translational pause and secA regulation, while mutations in the hydrophobic core region affect SecM secretion as well as translational pausing and secA regulation. In addition, mutational analysis of the 3' end of secM allowed us to identify a conserved region that is required to promote the translational pause that appears to be operative at the peptide level. Together, our results provide direct support for the secM translational pause model of secA regulation, and they pinpoint key sequences within secM that promote this important regulatory system.

* Corresponding author. Mailing address: Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT 06459. Phone: (860) 685-3556. Fax: (860) 685-2141. E-mail: doliver{at}wesleyan.edu.

Journal of Bacteriology, May 2002, p. 2360-2369, Vol. 184, No. 9
0021-9193/02/$04.00+0     DOI: 10.1128/JB.184.9.2360-2369.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

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  • Rahman, M. S., Simser, J. A., Macaluso, K. R., Azad, A. F. (2005). Functional analysis of secA homologues from rickettsiae. Microbiology 151: 589-596 [Abstract] [Full Text]  
  • Collier, J., Bohn, C., Bouloc, P. (2004). SsrA Tagging of Escherichia coli SecM at Its Translation Arrest Sequence. J. Biol. Chem. 279: 54193-54201 [Abstract] [Full Text]  
  • Murakami, A., Nakatogawa, H., Ito, K. (2004). Translation arrest of SecM is essential for the basal and regulated expression of SecA. Proc. Natl. Acad. Sci. USA 101: 12330-12335 [Abstract] [Full Text]  
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