title: Enhancer-binding proteins with a forkhead-associated domain and the sigma54 regulon in Myxococcus xanthus fruiting body development.
abstract: In response to starvation, Myxococcus xanthus initiates a developmental program that results in the formation of spore-filled, multicellular fruiting bodies. Many developmentally regulated genes in M. xanthus are transcribed from sigma(54) promoters, and these genes require enhancer-binding proteins. Here we report the finding of an unusual group of 12 genes encoding sigma(54)-dependent enhancer-binding proteins containing a forkhead-associated (FHA) domain as their N-terminal sensory domain. FHA domains in other proteins recognize phosphothreonine residues. An insertion mutation in one of these genes, Mx4885, caused a cell autonomous aggregation and sporulation defect. In-frame deletion mutants showed that the FHA domain is necessary for proper Mx4885 function. The altered pattern of developmental gene expression in the mutant implied that Mx4885 is on the pathway of response to the morphogenetic C-signal. Immunoblots specific for C-signal and FruA imply that the site of Mx4885 action is downstream of FruA synthesis on the C-signal transduction pathway. Mx4885 may help to coordinate the level of intracellular phosphorylated FruA (FruA-P) with the level of C-signal displayed on the signal donor cell. Because FHA domains respond to phosphothreonine-containing proteins, these results suggest a regulatory link to the abundant Ser/Thr protein kinases in M. xanthus.
authors.affiliation: Department of Biochemistry, Stanford University, Stanford, CA 94305, USA.
authors.forename: Lars
authors.initials: L
authors.lastname: Jelsbak
authors.forename: Michael
authors.initials: M
authors.lastname: Givskov
authors.forename: Dale
authors.initials: D
authors.lastname: Kaiser
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000502:physiology*; D012321:DNA-Directed RNA Polymerases / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D018507:Gene Expression Regulation, Developmental; D008969:Molecular Sequence Data; D016941:Myxococcus xanthus / Q000235:genetics / Q000254:growth & development*; D016366:Open Reading Frames; D011401:Promoter Regions, Genetic; D051877:RNA Polymerase Sigma 54; D018085:Regulon; D012808:Sigma Factor / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D013171:Spores, Bacterial / Q000502:physiology; D014157:Transcription Factors / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C104848:FruA protein, Myxococcus xanthus; D012808:Sigma Factor; D014157:Transcription Factors; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54