title: The sigmaR regulon of Streptomyces coelicolor A32 reveals a key role in protein quality control during disulphide stress.
abstract: Diamide is an artificial disulphide-generating electrophile that mimics an oxidative shift in the cellular thiol-disulphide redox state (disulphide stress). The Gram-positive bacterium Streptomyces coelicolor senses and responds to disulphide stress through the sigma(R)-RsrA system, which comprises an extracytoplasmic function (ECF) sigma factor and a redox-active anti-sigma factor. Known targets that aid in the protection and recovery from disulphide stress include the thioredoxin system and genes involved in producing the major thiol buffer mycothiol. Here we determine the global response to diamide in wild-type and sigR mutant backgrounds to understand the role of sigma(R) in this response and to reveal additional regulatory pathways that allow cells to cope with disulphide stress. In addition to thiol oxidation, diamide was found to cause protein misfolding and aggregation, which elicited the induction of the HspR heat-shock regulon. Although this response is sigma(R)-independent, sigma(R) does directly control Clp and Lon ATP-dependent AAA(+) proteases, which may partly explain the reduced ability of a sigR mutant to resolubilize protein aggregates. sigma(R) also controls msrA and msrB methionine sulphoxide reductase genes, implying that sigma(R)-RsrA is responsible for the maintenance of both cysteine and methionine residues during oxidative stress. This work shows that the sigma(R)-RsrA system plays a more significant role in protein quality control than previously realized, and emphasizes the importance of controlling the cellular thiol-disulphide redox balance.
authors.affiliation: Department of Chemistry and Biochemistry, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK.
authors.forename: Dimitris
authors.initials: D
authors.lastname: Kallifidas
authors.affiliation: Department of Chemistry and Biochemistry, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK.
authors.forename: Derek
authors.initials: D
authors.lastname: Thomas
authors.affiliation: Department of Chemistry and Biochemistry, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK.
authors.forename: Phillip
authors.initials: P
authors.lastname: Doughty
authors.affiliation: Department of Chemistry and Biochemistry, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK.
authors.forename: Mark S B
authors.initials: MSB
authors.lastname: Paget
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003958:Diamide / Q000494:pharmacology*; D004220:Disulfides / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000235:genetics; D017510:Protein Folding / Q000187:drug effects; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012313:RNA / Q000235:genetics; D018085:Regulon; D012097:Repressor Proteins / Q000235:genetics; D012808:Sigma Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D048372:Streptomyces coelicolor / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004220:Disulfides; D006360:Heat-Shock Proteins; C108444:HspR protein, bacteria; D011506:Proteins; D012097:Repressor Proteins; C121147:RsrA protein, Streptomyces coelicolor; D012808:Sigma Factor; D014157:Transcription Factors; D003958:Diamide; D012313:RNA