Organization and regulation of the genes for nitrogen fixation in Rhodopseudomonas capsulata: Progress report, June 5, 1987-June 4, 1988
We have cloned a number of fragments of DNA containing genes necessary for nitrogen fixation from the photosynthetic bacterium Rhodobacter capsulatus. The nif genes are locally clustered but the clusters are on non-neighboring DNA restriction fragments. We sought to determine the physical linkage of these fragments, to determine their relationship with the corresponding nif genes of Klebsiella, and to determine the nucleotide sequence of some of the fragments. So far we have identified six or seven regulatory genes among these, using a nifH::lac fusion. Four of the regulatory genes are required for expression of nifH. Two of these, nifR1 and nifR2, have sequences homologous to ntrC and ntrB of enteric bacteria. A third, nifR4, has sequence homology, in the C-terminal region, to the ntrA genes of Rhizobium and Klebsiella. Constitutive expression of nifR4 in R. capsulatus, from a plasmid clone, complemented a nifR4 chromosomal mutant but not a nifR1 mutant. Moreover, both oxygen and ammonia regulation of nitrogenase were maintained under these conditions. These results are consistent with a model requiring both nifR1 and nifR4 for nitrogenase gene expression; they rule out our earlier suggestion that nifR1 is needed only to turn on nifR4. Current efforts are focused on the purification of RNA polymerase and the products of nifR1, nifR2, and nifR4 to study nif gene transcription in vitro, particularly with the goal of determining the role of DNA supercoiling in transcription.
- Research Organization:
- Chicago Univ., IL (USA)
- DOE Contract Number:
- FG02-86ER13546
- OSTI ID:
- 5658027
- Report Number(s):
- DOE/ER/13546-2; ON: DE88005838
- Country of Publication:
- United States
- Language:
- English
Similar Records
[Organization and regulation of the genes for nitrogen fixation in Rhodopseudomonas capsulata]. Progress report, [June 5, 1989--June 4, 1991]
(Organization and regulation of the genes for nitrogen fixation in Rhodopseudomonas capsulata)
Related Subjects
59 BASIC BIOLOGICAL SCIENCES
GENE OPERONS
DNA SEQUENCING
DNA-CLONING
NITROGENASE
RNA POLYMERASES
FRACTIONATION
GENE MUTATIONS
NITROGEN FIXATION
NUCLEOPROTEINS
PHOTOSYNTHETIC BACTERIA
PROGRESS REPORT
RHODOPSEUDOMONAS
BACTERIA
CLONING
DOCUMENT TYPES
ENZYMES
MICROORGANISMS
MUTATIONS
NITRO-GROUP DEHYDROGENASES
NUCLEOTIDYLTRANSFERASES
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PHOSPHORUS-GROUP TRANSFERASES
POLYMERASES
PROTEINS
SEPARATION PROCESSES
STRUCTURAL CHEMICAL ANALYSIS
TRANSFERASES
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