title: Involvement of the multidomain regulatory protein XynR in positive control of xylanase gene expression in the ruminal anaerobe Prevotella bryantii B(1)4.
abstract: The xylanase gene cluster from the rumen anaerobe Prevotella bryantii B(1)4 was found to include a gene (xynR) that encodes a multidomain regulatory protein and is downstream from the xylanase and beta-xylosidase genes xynA and xynB. Additional genes identified upstream of xynA and xynB include xynD, which encodes an integral membrane protein that has homology with Na:solute symporters; xynE, which is related to the genes encoding acylhydrolases and arylesterases; and xynF, which has homology with the genes encoding alpha-glucuronidases. XynR includes, in a single 833-amino-acid polypeptide, a putative input domain unrelated to other database sequences, a likely transmembrane domain, histidine kinase motifs, response regulator sequences, and a C-terminal AraC-type helix-turn-helix DNA binding domain. Two transcripts (3.7 and 5.8 kb) were detected with a xynA probe, and the start site of the 3.7-kb transcript encoding xynABD was mapped to a position upstream of xynD. The DNA binding domain of XynR was purified after amplification and overexpression in Escherichia coli and was found to bind to a 141-bp DNA fragment from the region immediately upstream of xynD. In vitro transcription assays demonstrated that XynR stimulates transcription of the 3.7-kb transcript. We concluded that XynR acts as a positive regulator that activates expression of xynABD in P. bryantii B(1)4. This is the first regulatory protein that demonstrates significant homology with the two-component regulatory protein superfamily and has been shown to be involved in the regulation of polysaccharidase gene expression.
authors.affiliation: Laboratory of Animal Science, Kyoto Prefectural University, Shimogamo, Kyoto 606-8522, Japan.
authors.forename: Kohji
authors.initials: K
authors.lastname: Miyazaki
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Miyamoto
authors.forename: Derry K
authors.initials: DK
authors.lastname: Mercer
authors.forename: Tatsuaki
authors.initials: T
authors.lastname: Hirase
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Martin
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Kojima
authors.forename: Harry J
authors.initials: HJ
authors.lastname: Flint
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D021901:DNA, Intergenic; D043364:Endo-1,4-beta Xylanases; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D019077:Helix-Turn-Helix Motifs; D005810:Multigene Family; D018720:Prevotella / Q000235:genetics* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012418:Ruminants / Q000382:microbiology; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D043325:Xylan Endo-1,3-beta-Xylosidase; D014995:Xylosidases / Q000235:genetics* / Q000378:metabolism; D001617:beta-Glucosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D021901:DNA, Intergenic; D015534:Trans-Activators; D014995:Xylosidases; D001617:beta-Glucosidase; D043325:Xylan Endo-1,3-beta-Xylosidase; D043364:Endo-1,4-beta Xylanases