title: An anti-antisigma factor in the response of the bacterium Myxococcus xanthus to blue light.
abstract: Cells of the Gram-negative bacterium Myxococcus xanthus respond to blue light by producing carotenoids, pigments that play a protective role against the oxidative effects of light. Blue light triggers a network of regulatory actions that lead to the transcriptional activation of the structural genes for carotenoid synthesis. The product of carF, similar to a family of proteins of unknown function called Kua, is an early regulator of this process. Previous genetic data indicate that CarF participates in the light-dependent inactivation of the antisigma factor CarR. In the dark, CarR sequesters the ECF-sigma factor CarQ to the membrane, thereby preventing the activation of the structural genes for carotenoid synthesis. Using a bacterial two-hybrid system, we show here that both CarF and CarQ physically interact with CarR. These results, together with the finding that CarF is located at the membrane, support the hypothesis that CarF acts as an anti-antisigma factor. Comparison of CarF with other Kua proteins shows a remarkable conservation of a number of histidine residues. The effects on CarF function of several histidine to alanine substitutions and of the truncation of specific CarF domains are also reported here.
authors.affiliation: Departamento de Genética y Microbiología (Unidad Asociada al IQFR-CSIC), Facultad de Biología, Universidad de Murcia, 30100 Murcia, Spain.
authors.forename: Lilian
authors.initials: L
authors.lastname: Galbis-Martínez
authors.affiliation: Departamento de Genética y Microbiología (Unidad Asociada al IQFR-CSIC), Facultad de Biología, Universidad de Murcia, 30100 Murcia, Spain.
authors.forename: Marisa
authors.initials: M
authors.lastname: Galbis-Martínez
authors.affiliation: Departamento de Genética y Microbiología (Unidad Asociada al IQFR-CSIC), Facultad de Biología, Universidad de Murcia, 30100 Murcia, Spain.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Murillo
authors.affiliation: Departamento de Genética y Microbiología (Unidad Asociada al IQFR-CSIC), Facultad de Biología, Universidad de Murcia, 30100 Murcia, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Fontes
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D019677:Artificial Gene Fusion; D001426:Bacterial Proteins / Q000378:metabolism*; D002338:Carotenoids / Q000096:biosynthesis*; D002458:Cell Fractionation; D002462:Cell Membrane / Q000737:chemistry; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D017930:Genes, Reporter; D008027:Light; D008954:Models, Biological; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D016941:Myxococcus xanthus / Q000378:metabolism* / Q000502:physiology* / Q000528:radiation effects; D011485:Protein Binding; D025941:Protein Interaction Mapping; D017384:Sequence Deletion; D020798:Two-Hybrid System Techniques; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002338:Carotenoids; D001616:beta-Galactosidase