Design principles of the proteolytic cascade governing the σE-mediated envelope stress response in Escherichia coli: keys to graded, buffered, and rapid signal transduction

Rachna Chaba; Irina L. Grigorova; Julia M. Flynn; Tania A. Baker; Carol A. Gross

doi:10.1101/gad.1496707

Design principles of the proteolytic cascade governing the σ^E-mediated envelope stress response in Escherichia coli: keys to graded, buffered, and rapid signal transduction

¹ Department of Microbiology and Immunology, University of California at San Francisco, San Francisco, California 94158, USA;
² Graduate Group in Biophysics, University of California at San Francisco, San Francisco, California 94158, USA;
³ Department of Cell and Tissue Biology, University of California at San Francisco, San Francisco, California 94158, USA;
⁴ Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA;
⁵ Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

↵6 These authors contributed equally to this work.

Abstract

Proteolytic cascades often transduce signals between cellular compartments, but the features of these cascades that permit efficient conversion of a biological signal into a transcriptional output are not well elucidated. σ^E mediates an envelope stress response in Escherichia coli, and its activity is controlled by regulated degradation of RseA, a membrane-spanning anti-σ factor. Examination of the individual steps in this protease cascade reveals that the initial, signal-sensing cleavage step is rate-limiting; that multiple ATP-dependent proteases degrade the cytoplasmic fragment of RseA and that dissociation of σ^E from RseA is so slow that most free σ^E must be generated by the active degradation of RseA. As a consequence, the degradation rate of RseA is set by the amount of inducing signal, and insulated from the “load” on and activity of the cytoplasmic proteases. Additionally, changes in RseA degradation rate are rapidly reflected in altered σ^E activity. These design features are attractive as general components of signal transduction pathways governed by unstable negative regulators.

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Footnotes

↵7 Present address: Department of Microbiology and Immunology, University of California at San Francisco, 513 Parnassus Avenue, San Francisco, CA 94143, USA
↵8 Corresponding author.

↵8 E-MAIL cgross{at}cgl.ucsf.edu; FAX (415) 514-4080.
Article is online at http://www.genesdev.org/cgi/doi/10.1101/gad.1496707
- Received September 25, 2006.
- Accepted November 7, 2006.