The product of the nitrogen fixation regulatory gene nfrX of Azotobacter vinelandii is functionally and structurally homologous to the uridylyltransferase encoded by glnD in enteric bacteria.
We sequenced the nitrogen fixation regulatory gene nfrX from Azotobacter vinelandii, mutations in which cause a Nif- phenotype, and found that it encodes a 105-kDa protein (NfrX), the N terminus of which is highly homologous to that of the uridylyltransferase-uridylyl-removing enzyme encoded by glnD in Escherichia coli. In vivo complementation experiments demonstrate that the glnD and nfrX products are functionally interchangeable. A vinelandii nfrX thus appears to encode a uridylyltransferase-uridylyl-removing enzyme, and in this paper we report the first sequence of such a protein. The Nif- phenotype of nfrX mutants can be suppressed by a second mutation in a recently identified nifL-like gene immediately upstream of nifA in A. vinelandii. NifL mediates nif regulation in response to the N status in A. vinelandii, presumably by inhibiting NifA activator function as occurs in Klebsiella pneumoniae; thus, one role of NfrX is to modify, either directly or indirectly, the activity of the nifL product.
Agriculture and Food Research Council Nitrogen Fixation Laboratory, University of Sussex, Brighton, United Kingdom.
A
A
Contreras
M
M
Drummond
A
A
Bali
G
G
Blanco
E
E
Garcia
G
G
Bush
C
C
Kennedy
M
M
Merrick
D000225:Adenine / Q000378:metabolism; D000595:Amino Acid Sequence; D016948:Azotobacter vinelandii / Q000235:genetics*; D001483:Base Sequence; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D005798:Genes, Bacterial; D005809:Genes, Regulator; D005816:Genetic Complementation Test; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D009586:Nitrogen Fixation / Q000235:genetics*; D010641:Phenotype; D015183:Restriction Mapping; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D013489:Suppression, Genetic; D006599:UDPglucose-Hexose-1-Phosphate Uridylyltransferase / Q000235:genetics* / Q000378:metabolism
D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D006599:UDPglucose-Hexose-1-Phosphate Uridylyltransferase; D005974:Glutamate-Ammonia Ligase; D000225:Adenine