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Journal of Bacteriology, February 2008, p. 894-904, Vol. 190, No. 3
0021-9193/08/$08.00+0     doi:10.1128/JB.01759-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Secreted-Protein Response to {sigma}U Activity in Streptomyces coelicolor{triangledown} ,{dagger}

Nadria D. Gordon, Geri L. Ottaviano, Sarah E. Connell, Gregory V. Tobkin, Crystal H. Son, Sebastian Shterental, and Amy M. Gehring*

Department of Chemistry, Williams College, Williamstown, Massachusetts 01267

Received 3 November 2007/ Accepted 21 November 2007

The filamentous bacterium Streptomyces coelicolor forms an aerial mycelium as a prerequisite to sporulation, which occurs in the aerial hyphae. Uncontrolled activity of the extracytoplasmic function sigma factor {sigma}U blocks the process of aerial mycelium formation in this organism. Using a green fluorescent protein transcriptional reporter, we have demonstrated that sigU transcription is autoregulated. We have defined a {sigma}U-dependent promoter sequence and used this to identify 22 likely {sigma}U regulon members in the S. coelicolor genome. Since many of these genes encode probable secreted proteins, we characterized the extracellular proteome of a mutant with high {sigma}U activity caused by disruption of rsuA, the presumed cognate anti-sigma factor of {sigma}U. This mutant secreted a much greater quantity and diversity of proteins than the wild-type strain. Peptide mass fingerprinting was used to identify 79 proteins from the rsuA mutant culture supernatant. The most abundant species, SCO2217, SCO0930, and SCO2207, corresponded to secreted proteins or lipoproteins of unknown functions whose genes are in the proposed {sigma}U regulon. Several unique proteases were also detected in the extracellular proteome of the mutant, and the levels of the protease inhibitor SCO0762 were much reduced compared to those of the wild type. Consequently, extracellular protease activity was elevated about fourfold in the rsuA mutant. The functions of the proteins secreted as a result of {sigma}U activity may be important for combating cell envelope stress and modulating morphological differentiation in S. coelicolor.

* Corresponding author. Mailing address: Dept. of Chemistry, Williams College, 47 Lab Campus Dr., Williamstown, MA 01267. Phone: (413) 597-3227. Fax: (413) 597-4116. E-mail: agehring{at}williams.edu

{triangledown} Published ahead of print on 7 December 2007.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, February 2008, p. 894-904, Vol. 190, No. 3
0021-9193/08/$08.00+0     doi:10.1128/JB.01759-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Kim, E. S., Song, J. Y., Kim, D. W., Chater, K. F., Lee, K. J. (2008). A Possible Extended Family of Regulators of Sigma Factor Activity in Streptomyces coelicolor. J. Bacteriol. 190: 7559-7566 [Abstract] [Full Text]  


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