Obg, an essential GTP binding protein of Bacillus subtilis, is necessary for stress activation of transcription factor sigma(B).
sigma(B), the general stress response sigma factor of Bacillus subtilis, is activated when intracellular ATP levels fall or the bacterium experiences environmental stress. Stress activates sigma(B) by means of a collection of regulatory kinases and phosphatases (the Rsb proteins), which catalyze the release of sigma(B) from an anti-sigma factor inhibitor. By using the yeast dihybrid selection system to identify B. subtilis proteins that could interact with Rsb proteins and act as mediators of stress signaling, we isolated the GTP binding protein, Obg, as an interactor with several of these regulators (RsbT, RsbW, and RsbX). B. subtilis depleted of Obg no longer activated sigma(B) in response to environmental stress, but it retained the ability to activate sigma(B) by the ATP responsive pathway. Stress pathway components activated sigma(B) in the absence of Obg if the pathway's most upstream effector (RsbT) was synthesized in excess to the inhibitor (RsbS) from which it is normally released after stress. Thus, the Rsb proteins can function in the absence of Obg but fail to be triggered by stress. The data demonstrate that Obg, or a process under its control, is necessary to induce the stress-dependent activation of sigma(B) and suggest that Obg may directly communicate with one or more sigma(B) regulators.
Department of Microbiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78284-7758, USA.
J M
JM
Scott
W G
WG
Haldenwang
D000255:Adenosine Triphosphate / Q000378:metabolism; D001412:Bacillus subtilis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D001426:Bacterial Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005838:Genotype; D006360:Heat-Shock Proteins / Q000378:metabolism; D007700:Kinetics; D008954:Models, Biological; D010957:Plasmids; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012808:Sigma Factor / Q000378:metabolism*; D013171:Spores, Bacterial / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism
D001426:Bacterial Proteins; D002352:Carrier Proteins; D006360:Heat-Shock Proteins; C090542:Obg GTP-binding protein, Bacteria; D011994:Recombinant Proteins; C080358:RsbW protein, bacteria; C079011:SigB protein, Bacteria; D012808:Sigma Factor; C080950:Spo0A protein, Bacillus subtilis; D014157:Transcription Factors; D000255:Adenosine Triphosphate; C119219:RsbT protein, Bacillus subtilis; D017346:Protein Serine-Threonine Kinases; D019204:GTP-Binding Proteins