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Vol. 173, No. 1JOURNAL OF BACTERIOLOGY, Jan. 1991, p. 382-390 0021-9193/91/010382-09$02.00/0
 

Summary: Vol. 173, No. 1JOURNAL OF BACTERIOLOGY, Jan. 1991, p. 382-390
0021-9193/91/010382-09$02.00/0
Copyright C 1991, American Society for Microbiology
Aerobic Inactivation of Rhizobium meliloti NifA in Escherichia coli
Is Mediated by lon and Two Newly Identified Genes,
snoB and snoC
EVA HUALA,t ANNE L. MOON,t AND FREDERICK M. AUSUBEL*
Department of Genetics, Harvard Medical School, and Department ofMolecular Biology,
Massachusetts General Hospital, Boston, Massachusetts 02114
Received 16 July 1990/Accepted 12 October 1990
The Rhizobium meliloti NifA protein is an oxygen-sensitive transcriptional regulator of nitrogen fixation
genes. Regulation of NifA activity by oxygen occurs at the transcriptional level through fixLJ and at the
posttranslational level through the sensitivity of NifA to oxygen. We have previously reported that the NifA
protein is sensitive to oxygen in Escherichia coli as well as in R. meliloti. To investigate whether the
posttranslational regulation of NifA is dependent on host factors conserved between R. meliloti and E. coli, we
carried out a TnS mutagenesis of E. coli and isolated mutants with increased NifA activity under aerobic
conditions. Fifteen insertion mutations occurred at three unlinked loci. One locus is the previously character-
ized Ion gene; the other two loci, which we have named snoB and snoC, define previously uncharacterized E.
coli genes. The products of snoC and Ion affect the rate of NifA degradation, whereas the product of snoB may
affect both NifA degradation and inactivation. A snoB lon double mutant showed a higher level of NifA

  

Source: Ausubel, Frederick M. - Department of Genetics, Harvard University

 

Collections: Biology and Medicine