title: Characterization of nifB, nifS, and nifU genes in the cyanobacterium Anabaena variabilis: NifB is required for the vanadium-dependent nitrogenase.
abstract: Anabaena variabilis ATCC 29413 is a heterotrophic, nitrogen-fixing cyanobacterium containing both a Mo-dependent nitrogenase encoded by the nif genes and V-dependent nitrogenase encoded by the vnf genes. The nifB, nifS, and nifU genes of A. variabilis were cloned, mapped, and partially sequenced. The fdxN gene was between nifB and nifS. Growth and acetylene reduction assays using wild-type and mutant strains indicated that the nifB product (NifB) was required for nitrogen fixation not only by the enzyme encoded by the nif genes but also by the enzyme encoded by the vnf genes. Neither NifS nor NifU was essential for nitrogen fixation in A. variabilis.
authors.affiliation: Department of Biology, University of Missouri--St. Louis 63121.
authors.forename: E M
authors.initials: EM
authors.lastname: Lyons
authors.forename: T
authors.initials: T
authors.lastname: Thiel
mesh_terms: D000114:Acetylene / Q000378:metabolism; D017033:Anabaena / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics*; D003001:Cloning, Molecular; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D016296:Mutagenesis; D009586:Nitrogen Fixation / Q000235:genetics; D009591:Nitrogenase / Q000235:genetics* / Q000378:metabolism; D015183:Restriction Mapping; D014158:Transcription, Genetic; D014639:Vanadium / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C092498:NifB protein, Bacteria; C088637:NifU protein, Bacteria; C080001:nifS protein, Bacteria; D014639:Vanadium; D009591:Nitrogenase; D000114:Acetylene