title: HoxA is a transcriptional regulator for expression of the hup structural genes in free-living Bradyrhizobium japonicum.
abstract: A chromosomally integrated Bradyrhizobium japonicum hoxA mutant is unable to oxidize hydrogen in free-living conditions. Derepressing conditions that induce hydrogenase activity in free-living, wild-type B. japonicum cells cannot induce expression of the hydrogenase structural genes in the hoxA mutant. The DNA-binding capacity of HoxA at the hup promoter region was studied by means of gel retardation. Both heterotrophically growing cells and cells induced to express hydrogenase activity contain a protein that specifically binds to the hup promoter region. Crude protein extracts isolated from a B. japonicum hoxA mutant do not contain this binding compound. The HoxA protein was overexpressed in E. coli and isolated in the form of a maltose-binding protein (MBP)-HoxA fusion. The MBP-HoxA hybrid protein specifically bound to a 50 bp region of the hupSL promoter known to be important for regulation of hupSL expression.
authors.affiliation: F. A. Janssens Laboratory of Genetics, K. U. Leuven, Heverlee, Belgium.
authors.forename: C
authors.initials: C
authors.lastname: Van Soom
authors.forename: P
authors.initials: P
authors.lastname: de Wilde
authors.forename: J
authors.initials: J
authors.lastname: Vanderleyden
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics / Q000276:immunology; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics; D002874:Chromosome Mapping; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D018398:Homeodomain Proteins; D006864:Hydrogenase / Q000235:genetics* / Q000378:metabolism; D033902:Periplasmic Binding Proteins; D010957:Plasmids; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D011995:Recombination, Genetic; D012231:Rhizobium / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics* / Q000276:immunology / Q000502:physiology*; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D018398:Homeodomain Proteins; C461619:MalE protein, E coli; D033902:Periplasmic Binding Proteins; D015534:Trans-Activators; C088144:HoxA protein; D006864:Hydrogenase; D001616:beta-Galactosidase