title: Characterization and nucleotide sequence of a novel gene fixW upstream of the fixABC operon in Rhizobium leguminosarum.
abstract: On the Rhizobium leguminosarum PRE sym plasmid, fixABC and a novel gene fixW were identified upstream of the regulatory gene nifA. The molecular masses of FixABC, 29, 44 and 50 kDa respectively, were estimated by polyacrylamide gel electrophoresis (PAGE) and of FixW, 25 kDa, by PAGE and nucleotide sequencing. Hybridization studies using bacteroid mRNA as a probe showed that fixABC is one operon which can be transcribed independently of fixW. Nucleotide sequencing revealed that both fixW and fixA are preceded by a nif consensus promoter. The fixA promoter partly overlaps the 3'-terminal coding region of fixW, indicating that readthrough from fixW into fixA is possible. Two open reading frames, ORF71 and ORF79, precede fixW and form one operon with fixW. ORF71 contains sequences homologous to the fixA promoter and 5'-terminal coding region. One more duplication of fixA sequences was detected, also located within the sym plasmid nif/fix clusters. One duplication of fixW sequences was found. No fixW homologue could be found in other nitrogen fixing organisms except in a number of R. leguminosarum strains.
authors.affiliation: Department of Molecular Biology, Agricultural University, Wageningen, The Netherlands.
authors.forename: J G
authors.initials: JG
authors.lastname: Hontelez
authors.forename: R K
authors.initials: RK
authors.lastname: Lankhorst
authors.forename: P
authors.initials: P
authors.lastname: Katinakis
authors.forename: R C
authors.initials: RC
authors.lastname: van den Bos
authors.forename: A
authors.initials: A
authors.lastname: van Kammen
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D004262:DNA Restriction Enzymes; D004251:DNA Transposable Elements; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation; D015183:Restriction Mapping; D012231:Rhizobium / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D004251:DNA Transposable Elements; D004262:DNA Restriction Enzymes