title: XacR - a novel transcriptional regulator of D-xylose and L-arabinose catabolism in the haloarchaeon Haloferax volcanii.
abstract: The haloarchaeon Haloferax volcanii degrades D-xylose and L-arabinose via oxidative pathways to α-ketoglutarate. The genes involved in these pathways are clustered and were transcriptionally upregulated by both D-xylose and L-arabinose suggesting a common regulator. Adjacent to the gene cluster, a putative IclR-like transcriptional regulator, HVO_B0040, was identified. It is shown that HVO_B0040, designated xacR, encodes an activator of both D-xylose and L-arabinose catabolism: in ΔxacR cells, transcripts of genes involved in pentose catabolism could not be detected; transcript formation could be recovered by complementation, indicating XacR dependent transcriptional activation. Upstream activation promoter regions and nucleotide sequences that were essential for XacR-mediated activation of pentose-specific genes were identified by in vivo deletion and scanning mutagenesis. Besides its activator function XacR acted as repressor of its own synthesis: xacR deletion resulted in an increase of xacR promoter activity. A palindromic sequence was identified at the operator site of xacR promoter, and mutation of this sequence also resulted in an increase and thus derepression of xacR promoter activity. It is concluded that the palindromic sequence represents the binding site of XacR as repressor. This is the first report of a transcriptional regulator of pentose catabolism in the domain of archaea.
authors.affiliation: Institut für Allgemeine Mikrobiologie, Christian-Albrechts-Universität Kiel, Am Botanischen Garten 1-9, Kiel, D-24118, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Johnsen
authors.forename: Jan-Moritz
authors.initials: JM
authors.lastname: Sutter
authors.forename: Anne-Christine
authors.initials: AC
authors.lastname: Schulz
authors.forename: Julia-Beate
authors.initials: JB
authors.lastname: Tästensen
authors.forename: Peter
authors.initials: P
authors.lastname: Schönheit
mesh_terms: D000595:Amino Acid Sequence; D001089:Arabinose / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D050260:Carbohydrate Metabolism / Q000235:genetics*; D019641:DNA, Archaeal / Q000032:analysis / Q000235:genetics; D019848:Gene Expression Regulation, Archaeal; D019622:Haloferax volcanii / Q000235:genetics* / Q000378:metabolism*; D055029:Inverted Repeat Sequences / Q000235:genetics; D007656:Ketoglutaric Acids / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D011401:Promoter Regions, Genetic / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion / Q000235:genetics; D014158:Transcription, Genetic / Q000235:genetics; D015533:Transcriptional Activation / Q000235:genetics; D014994:Xylose / Q000378:metabolism*
chemical_list: D019641:DNA, Archaeal; D007656:Ketoglutaric Acids; D014994:Xylose; D001089:Arabinose