title: NblR is a novel one-component response regulator in the cyanobacterium Synechococcus elongatus PCC 7942.
abstract: A response regulator, NblR, of the cyanobacterium Synechococcus elongatus PCC 7942 is known to induce expression of the nblA gene, a key factor in phycobilisome degradation (bleaching) under nutrient-deprivation conditions. In this study, we observed phosphorylation-independent regulation of NblR activity. We constructed a mutant strain expressing NblR (D57A), in which a putative phospho-accepting Asp-57 was replaced with Ala residue. Under nitrogen deprivation, this strain exhibited the typical bleaching phenotype observed in wild-type cells. Moreover, in the mutant, the nblA transcript accumulated at a level similar to that of the wild type. Our results indicate that activation of NblR is independent of phosphorylation, if any, by a cognate histidine kinase. Screening of proteins interacting with NblR by yeast two-hybrid analysis revealed two candidates, MreC and NarB, suggesting a novel mechanism that activates NblR, or other functions of the response regulator.
authors.affiliation: Department of Bioscience, Tokyo University of Agriculture, Sakuragaoka, Setagaya-ku, Tokyo 156-8502, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kato
authors.forename: Taku
authors.initials: T
authors.lastname: Chibazakura
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yoshikawa
mesh_terms: D000595:Amino Acid Sequence; D001224:Aspartic Acid / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015698:Genomic Library; D008969:Molecular Sequence Data; D009154:Mutation; D009584:Nitrogen / Q000172:deficiency; D010766:Phosphorylation; D045524:Phycobilisomes / Q000378:metabolism; D012313:RNA / Q000235:genetics; D016415:Sequence Alignment; D013379:Substrate Specificity; D046940:Synechococcus / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: D001426:Bacterial Proteins; C062061:MreC protein, Bacteria; C114424:NblR protein, Synechococcus sp.; D045524:Phycobilisomes; D014157:Transcription Factors; D001224:Aspartic Acid; D012313:RNA; D009584:Nitrogen