Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mol- mutants of Klebsiella pneumoniae requiring high levels of molybdate for nitrogenase and nitrate reductase activity were characterized. The effects of mol mutations on nitrogenase activity were very similar to those caused by nifQ mutations. Mol- mutants of K. pneumoniae appear to be equivalent to ChlD- mutants of Escherichia coli.
 ...
PMID:Mol- mutants of Klebsiella pneumoniae requiring high levels of molybdate for nitrogenase activity. 389 91

NifQ- and Mol- mutants of Klebsiella pneumoniae show an elevated molybdenum requirement for nitrogen fixation. Substitution of cystine for sulfate as the sulfur source in the medium reduced the molybdenum requirement of these mutants to levels required by the wild type. Cystine also increased the intracellular molybdenum accumulation of NifQ- and Mol- mutants. Cystine did not affect the molybdenum requirement or accumulation in wild-type K. pneumoniae. Sulfate transport and metabolism in K. pneumoniae were repressed by cystine. However, the effect of cystine on the molybdenum requirement could not be explained by an interaction between sulfate and molybdate at the transport level. Cystine increased the molybdenum requirement of Mol- mutants for nitrate reductase activity by at least 100-fold. Cystine had the same effect on the molybdenum requirement for nitrate reductase activity in Escherichia coli ChlD- mutants. This shows that cystine does not have a generalized effect on molybdenum metabolism. Millimolar concentrations of molybdate inhibited nitrogenase and nitrate reductase derepression with sulfate as the sulfur source, but not with cystine. The inhibition was the result of a specific antagonism of sulfate metabolism by molybdate. The effects of nifQ and mol mutations on nitrogenase could be suppressed either by the addition of cystine or by high concentrations of molybdate. This suggests that a sulfur donor and molybdenum interact at an early step in the biosynthesis of the iron-molybdenum cofactor. This interaction might occur nonenzymatically when the levels of the reactants are high.
 ...
PMID:Biosynthesis of the iron-molybdenum cofactor and the molybdenum cofactor in Klebsiella pneumoniae: effect of sulfur source. 390 65

A number of mutants have been isolated which affect regulation of the nitrogen fixation (nif) gene cluster in Klebsiella pneumoniae and all of which are linked to glnA, the structural gene for glutamine synthetase (G.S.). These mutants were classified on the basis of their G.S. and nitrogenase activities in conditions of nitrogen limitation and excess. The plasmid R68.45 was then used to generate a number of R-primes carrying the glnA region of the K. pneumoniae chromosome. One of these R-primes (pGE10) was subsequently used in complementation analysis and by isolation of transposon-induced insertion mutations in pGE10 we have demonstrated the existence of a gene, glnG, closely linked to glnA. Mutations in glnG have a similar phenotype to glnG mutants described in Escherichia coli (Pahel and Tyler 1979) and Salmonella typhimurium (Kustu et al. 1979) in that substantially reduce G.S. activity but are not glutamine auxotrophs. GlnG mutants have very low nitrogenase activity indicating that the glnG product may be involved regulation of the nif gene cluster in K. pneumoniae.
Mol Gen Genet 1981
PMID:Complementation analysis of glnA-linked mutations which affect nitrogen fixation in Klebsiella pneumoniae. 612 Apr 41

A new selection procedure has been developed for isolating prototrophic relaxed mutants of Klebsiella pneumoniae. Two mutants were isolated. One of them showed a fully relaxed phenotype, while the other one behaved in a semi-relaxed way. The wild-type strain, as well as the rel mutants exerted similar patterns to their E. coli counterparts in RNA, protein, ppGpp and pppGpp accumulation during amino starvation, carbon source shift-down and nitrogen starvation. Both mutants became stringent after introducing an F'-factor carrying the relA+ allele from Escherichia coli. The relaxed phenotype could be recovered by curing the F'-factor. Some of the pleiotropic consequences of rel mutations found in E. coli are present in the Klebsiella mutants also while some of them are absent. The mutants are defective in dinitrogen fixation after the exhaustion of limiting ammonium from the culture medium. However, their merodiploid derivatives, carrying the E. coli relA+ allele, showed the wild-type level of nitrogenase activity under the same conditions.
Mol Gen Genet 1981
PMID:Isolation and characterization of prototrophic relaxed mutants of Klebsiella pneumoniae. 626 22

A new method of estimation of the distance RLM between the nitroxide spin label (NSL) and the paramagnetic metal ions (PMI), such as Co2+, Ni2+, Cu2+, Mn2+, VO2+, Cr3+, Fe3+ is suggested. The influence of the longitudinal relaxation time T1 of the PMI on the line shape of the NSL at 77 degrees K has been studied. It was found that the efficiency of the dipole-dipole interaction between NSL and PMI depends strongly on the T1 value of the PMI. Measurements of the RLM for 4 spin-labelled proteins (haemoglobin, nitrogenase, cytochrome P450 and Ca2+-dependent ATPase) by three various methods have proved the correctness of the new method and also its simplicity.
Mol Biol (Mosk)
PMID:[New method for measuring the distances between the nitroxide spin label and paramagnetic metal ions in macromolecules]. 626 67

Restriction endonuclease-digested deoxyribonucleic acid (DNA) from 17 slow-growing Rhizobium strains was hybridized with 32P-labeled DNA of the Klebsiella pneumoniae nitrogenase structural gene (nifKDH) region. Sixteen of these strains contained two or more fragments that were homologous to K. pneumoniae nifKDH after cleavage with EcoRI or HindIII. Hybridization with nifKDH subclones revealed that most of the Rhizobium fragments were homologous to the HindIII-EcoRI portion of nifKDH (corresponding to the nifDH region), although fragments homologous to the EcoRI-HindIII portion of nifKDH (corresponding to the nifK region) were also present. Comigrating nif-homologous restriction endonuclease fragments were observed for strains isolated from different geographic locations and from nodules of different plant species. Nearly identical hybridization patterns were obtained for five R. japonicum strains which clearly differed in the pattern of restriction endonuclease fragments from their chromosomal DNA. This indicates that there is a high degree of conservation of DNA sequence surrounding the region of nif homology in these strains.
J Mol Appl Genet 1983
PMID:Conservation of DNA regions adjacent to nifKDH homologous sequences in diverse slow-growing Rhizobium strains. 631 24

In order to study the structural organization and regulation of the expression of the nitrogenase gene cluster in Rhizobium leguminosarum PRE we selected relevant subfragments of the sym-plasmid from clone banks by homology with R. meliloti nif-genes. Site-directed Tn5 mutagenesis was applied to a nif DH-specific clone and subsequently the transposon insertions were transferred back into the wild-type rhizobial genome by homologous recombination. Phenotypic effects of Tn5 mutations in the region of the structural nif-genes were determined by measuring acetylene reduction in nodulated plants and by immunological analysis of bacteroid-specific proteins. The localization of Tn5 insertion sites was in accordance with observed consequences: two genotypically different Tn5-induced mutations within nif D caused repression of CI alpha and beta synthesis and a strong reduction of CII production, thus resulting in a Fix- phenotype. Expression of different cloned Rhizobium DNA inserts, bearing nif K, nif D, nif H, or nif DH, was achieved in Escherichia coli minicells dependent upon the presence of a strong upstream vector promoter sequence. Gene products were identified by immunoprecipitation with specific antisera. Endogenous rhizobial transcriptional start signals in one case (nif H) seemed to be recognized at a low rate by the E. coli system; in contrast, Rhizobium ribosome binding sites for all three structural nif-genes functioned normally in minicells. The approximate location of the coding regions for nif KDH genes was determined and found to be contiguous.
J Mol Appl Genet 1984
PMID:Molecular cloning and functional characterization of Rhizobium leguminosarum structural nif-genes by site-directed transposon mutagenesis and expression in Escherichia coli minicells. 633 Feb 64

A set of 19 symbiotic mutants of Rhizobium meliloti obtained by a Tn5 "suicide plasmid" mutagenesis procedure was characterized genetically and physically. As part of this characterization, we showed that R. meliloti strain 1021, like other R. meliloti strains, contains a very large indigenous plasmid (greater than 300 Md) that carries the structural genes for nitrogenase (nifHDK genes). Among the 19 symbiotic mutations studied, at least six were shown to reside on the megaplasmid. By a "walking procedure" we obtained from a cosmid clone bank a set of overlapping cosmids that contained megaplasmid sequences contiguous to nifHDK. A 90 kb region of contiguous DNA from these cosmids was used to probe the mutant strains for rearrangements within this region. The same six mutations that were located on the megaplasmid mapped within the 90 kb region examined, which included the structural genes for nitrogenase (nifHDK). A majority of the mutations characterized in this study could not be correlated with a bona fide Tn5 insertion into a symbiotic gene.
J Mol Appl Genet 1983
PMID:Physical and genetic characterization of Rhizobium meliloti symbiotic mutants. 636 87

By DNA hybridisation, restriction fragments of genomic DNA from Azotobacter chroococcum and A. vinelandii bearing sequences homologous to Klebsiella pneumoniae nitrogenase structural genes were detected. These were different in the two species and inconsistent with the arrangement of the homologous sequences as a contiguous cluster of unique genes. The use of a DNA probe specific for nifH showed that in A. chroococcum two nifH-like sequences were present in the genome. From gene libraries for A. chroococcum, several recombinant cosmid clones bearing nif genes were identified and physically mapped. One copy of the nifH-like sequences was closely linked to nifD and K, the order of genes being as for K. pneumoniae. This cluster was sub-cloned into the broad host-range vector pKT230. The resultant plasmid complemented for C2H2-reduction but not growth in N2 several Nif- mutants of A. vinelandii and K. pneumoniae and also abolished growth in N2 in Nif+ parents. The inhibition was ascribed to a short region adjacent to nifH, which probably corresponds to the promoter as its inhibitory affects were alleviated by provision of K. pneumoniae nifA in multiple copies. 3 sizes of transcripts are produced from the region containing nifH and nifD of A. chroococcum in cultures derepressing for nif. A region bearing homology to a fragment of the K. pneumoniae nif cluster bearing nifV was identified 15 Kb away from nifHDK in A. chroococcum however the order of genes is probably similar to that of K. pneumoniae.
Mol Gen Genet 1984
PMID:Cloning and organisation of some genes for nitrogen fixation from Azotobacter chroococcum and their expression in Klebsiella pneumoniae. 639 56

The decoupling possibility of ATPase reaction with electron transfer process in the time of nitrogenase photolysis by lambda 435 nm light has been established. The COOH and the possibility of imidazole groups have been revealed in nitrogenase ATPase centre by methods of chemical modification. The reaction of direct 18O-exchange between inorganic phosphate and medium water was discovered, proceeding under reverse hydrolysis of acylphosphate bond, formed by phosphorylation of COOH-group in ATPase centre. Direct 18O-exchange was shown to be stimulated by ATP and ADP, but to be insensitive to GTP, CTP, AMP-nucleotide which are not ATPase centre substrates. The coupling mechanism of ATPase reaction with electron transfer is suggested; it is based on the possibility of compulsory protonation of Fe-S-cluster at the expense of proton transfer from the imidazole site, facilitating additional electron transfer under "superreduction" of nitrogenase component of the Mo-Fe-protein. It is assumed that this protonation is initiated by COOH-group of charge relay transfer with imidasole fragment.
Mol Biol (Mosk) 1980
PMID:[Role of adenosine triphosphatase on nitrogenase function]. 645 79


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>