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J. Bacteriol., Feb 1995, 1023-1029, Vol 177, No. 4
S Rech, U Deppenmeier and RP Gunsalus
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.
Copyright © 1995, American Society for Microbiology
Regulation of the molybdate transport operon, modABCD, of Escherichia coli in response to molybdate availability
Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90024.
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