Regulation of the molybdate transport operon, modABCD, of Escherichia coli in response to molybdate availability.
The mod (chlD) locus at 17 min on the Escherichia coli chromosome encodes a high-affinity molybdate uptake system. To further investigate the structure and regulation of these genes, the DNA region upstream of the previously identified modBC (chlJD) genes was cloned and sequenced. A single open reading frame, designated modA, was identified and appears to encode a periplasmic binding protein for the molybdate uptake system. To determine how the mod genes are regulated in response to molybdate, nitrate, and oxygen, we constructed a series of mod-lacZ operon fusions to the upstream region and introduced them in single copy onto the E. coli chromosome. Whereas molybdate limitation resulted in elevated mod-lacZ expression, neither oxygen nor nitrate had any significant effect on gene expression. A regulatory motif, CATAA, located at the modA promoter was identified and shown to be required for molybdate-dependent control of the modABCD operon. Mutations within this sequence resulted in nearly complete derepression of gene expression and suggest that transcription of the operon is mediated by a molybdenum-responsive regulatory protein.
Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90024.
S
S
Rech
U
U
Deppenmeier
R P
RP
Gunsalus
D000483:Alleles; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D001692:Biological Transport; D003067:Coenzymes; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D008565:Membrane Proteins / Q000235:genetics; D008667:Metalloproteins / Q000378:metabolism; D008969:Molecular Sequence Data; D008982:Molybdenum / Q000378:metabolism*; D000090006:Molybdenum Cofactors; D009154:Mutation; D009566:Nitrates / Q000494:pharmacology; D009876:Operon / Q000235:genetics*; D010100:Oxygen / Q000494:pharmacology; D010750:Phosphoproteins / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011494:Protein Kinases; D011621:Pteridines / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012097:Repressor Proteins / Q000235:genetics
D001426:Bacterial Proteins; D003067:Coenzymes; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D008667:Metalloproteins; D008982:Molybdenum; D000090006:Molybdenum Cofactors; D009566:Nitrates; D010100:Oxygen; D010750:Phosphoproteins; D011494:Protein Kinases; D011621:Pteridines; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C068477:ferric uptake regulating proteins, bacterial; C088708:narQ protein, E coli; C069780:NarL protein, E coli; C044659:molybdate; C022261:molybdopterin; C074787:narX protein, E coli