title: GerN, an antiporter homologue important in germination of Bacillus cereus endospores.
abstract: A homologue of the grmA spore germination gene of Bacillus megaterium and of a NaH-antiporter gene (napA) of Enterococcus hirae has been identified in Bacillus cereus 569 (ATCC 10876). The putative protein product has 58 and 43% amino acid identity with GrmA and NapA, respectively. Insertional inactivation of this B. cereus gene, named gerN, did not affect vegetative growth or sporulation. The null mutant spores were 30-fold slower to germinate in inosine (5 mM) but germinated almost normally in response to L-alanine (10 mM). The null mutant spores germinated after several hours with inosine as the sole germinant, but germination was asynchronous and the normal order of germination events was perturbed. At a suboptimal germinant concentration (50 microM), inosine germination was completely blocked in the mutant, while the rate of germination in 50 microM L-alanine was reduced to one-third of that of the wild type. The requirement for GerN function in the response to a particular germinant suggests that a germination receptor may have a specifically associated antiporter, which is required at the initiation of germination and which, in the case of the inosine receptor, is GerN. Since germination in suboptimal concentrations of L-alanine shows a delay, additional germination transporters may be required for optimal response at low germinant concentrations.
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom.
authors.forename: P D
authors.initials: PD
authors.lastname: Thackray
authors.forename: J
authors.initials: J
authors.lastname: Behravan
authors.forename: T W
authors.initials: TW
authors.lastname: Southworth
authors.forename: A
authors.initials: A
authors.lastname: Moir
mesh_terms: D055516:2S Albumins, Plant; D000409:Alanine / Q000378:metabolism; D000595:Amino Acid Sequence; D017920:Antiporters / Q000235:genetics* / Q000378:metabolism; D001409:Bacillus cereus / Q000502:physiology* / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001692:Biological Transport; D007288:Inosine / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010848:Picolinic Acids / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013171:Spores, Bacterial
chemical_list: D055516:2S Albumins, Plant; D017920:Antiporters; D001426:Bacterial Proteins; C419208:GerN protein, Bacillus cereus; C099513:GrmA protein, Bacillus megaterium; D008565:Membrane Proteins; D010848:Picolinic Acids; D010940:Plant Proteins; D007288:Inosine; C050363:napin protein, Brassica napus; D000409:Alanine; C004860:dipicolinic acid