Nucleotide sequences and mutational analysis of the structural genes for nitrogenase 2 of Azotobacter vinelandii.
The nucleotide sequence (6,559 base pairs) of the genomic region containing the structural genes for nitrogenase 2 (V nitrogenase) from Azotobacter vinelandii was determined. The open reading frames present in this region are organized into two transcriptional units. One contains vnfH (encoding dinitrogenase reductase 2) and a ferredoxinlike open reading frame (Fd). The second one includes vnfD (encoding the alpha subunit of dinitrogenase 2), vnfG (encoding a product similar to the delta subunit of dinitrogenase 2 from A. chroococcum), and vnfK (encoding the beta subunit of dinitrogenase 2). The 5'-flanking regions of vnfH and vnfD contain sequences similar to ntrA-dependent promoters. This gene arrangement allows independent expression of vnfH-Fd and vnfDGK. Mutant strains (CA80 and CA11.80) carrying an insertion in vnfH are still able to synthesize the alpha and beta subunits of dinitrogenase 2 when grown in N-free, Mo-deficient, V-containing medium. A strain (RP1.11) carrying a deletion-plus-insertion mutation in the vnfDGK region produced only dinitrogenase reductase 2.
Joerger
R D
RD
U.S. Department of Agriculture, North Carolina State University, Raleigh 27695-7615.
Loveless
T M
TM
Pau
R N
RN
Mitchenall
L A
LA
Simon
B H
BH
Bishop
P E
PE
D000595:Amino Acid Sequence; D001395:Azotobacter / Q000201:enzymology / Q000235:genetics*; D001483:Base Sequence; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D009591:Nitrogenase / Q000032:analysis / Q000235:genetics*
D009591:Nitrogenase