title: Immunolocalization of NblA, a protein involved in phycobilisome turnover, during heterocyst differentiation in cyanobacteria.
abstract: In unicellular non-diazotrophic cyanobacteria, NblA is a small polypeptide required for phycobilisome degradation during macronutrient limitation. In the filamentous N(2)-fixing Tolypothrix sp., a nblA gene (nblAI) lies upstream of the cpeBA operon that encodes phycoerythrin apoproteins. Using a specific anti-NblAI antibody it was found that in strains of Tolypothrix sp. NblAI abundance increases under nitrogen-limiting conditions but the protein is also present in cells grown in nitrogen-replete medium. Gold immunolabelling experiments showed that, upon a nitrogen shift-down, NblAI is preferentially located in the differentiated heterocysts, where O(2) evolution has to be shut off for nitrogenase to operate. The results lead to the proposal that NblAI is a necessary 'cofactor' but not the triggering factor that governs phycobilisome degradation in Tolypothrix sp.
authors.affiliation: Organismes Photosynthétiques et Environnement, CNRS FRE 2433, Département de Biologie, École Normale Supérieure, 46 rue d'Ulm, 75230 Paris Cedex 05, France.
authors.forename: Jesús A G Ochoa
authors.initials: JAGO
authors.lastname: de Alda
authors.affiliation: Organismes Photosynthétiques et Environnement, CNRS FRE 2433, Département de Biologie, École Normale Supérieure, 46 rue d'Ulm, 75230 Paris Cedex 05, France.
authors.forename: Christiane
authors.initials: C
authors.lastname: Lichtlé
authors.affiliation: Organismes Photosynthétiques et Environnement, CNRS FRE 2433, Département de Biologie, École Normale Supérieure, 46 rue d'Ulm, 75230 Paris Cedex 05, France.
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Thomas
authors.affiliation: Organismes Photosynthétiques et Environnement, CNRS FRE 2433, Département de Biologie, École Normale Supérieure, 46 rue d'Ulm, 75230 Paris Cedex 05, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Houmard
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003470:Culture Media; D000458:Cyanobacteria / Q000254:growth & development* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000378:metabolism / Q000494:pharmacology; D045524:Phycobilisomes / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D045524:Phycobilisomes; C426123:nblA protein, Synechocystis; D009584:Nitrogen