Regulation of the general stress response sigma factor σT by Lon-mediated proteolysis

• The Lon protease is widely conserved in both prokaryotic and eukaryotic organisms and fulfills important regulatory functions. Nevertheless, the number of identified Lon substrates is limited in most organisms, and the precise role of Lon in regulating these proteins is poorly understood. Here, we describe the α-proteobacterial general stress response sigma factor σT as a novel Lon substrate in Caulobacter crescentus. Based on previously published quantitative proteomics data, we find σT to be a promising putative Lon substrate and confirm a direct role of Lon in degrading σT. We show that Lon contributes to the downregulation of σT abundance under optimal conditions and during recovery from sucrose-induced osmotic stress. Furthermore, the presence of the Lon activity regulator LarA enhances Lon-mediated degradation of σT in vitro and reduces σT levels in vivo indicating a role of LarA in modulating Lon-mediated degradation of σT. Together, our results highlight the importance of Lon during the recovery phase following stress exposure by adjusting the concentrations of critical regulators of stress responses.

Subject headings

NATURVETENSKAP  -- Biologi -- Mikrobiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Microbiology (hsv//eng)

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

Keyword

regulated proteolysis

Lon protease

ECF sigma factor

general stress response

Caulobacter crescentus

Publication and Content Type

ref (subject category)

art (subject category)