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J. Bacteriol., Aug 1996, 5020-5023, Vol 178, No. 16
PJ Desai, A Angerer and CA Genco
The gene encoding Neisseria gonorrhoeae periplasmic binding protein FbpA
contains two regions whose sequences exhibit homology with the Escherichia
coli ferric uptake regulator protein (Fur) consensus binding sequence. In
this study, DNase I footprinting experiments were employed to characterize
the operator sequences within the fbpA promoter region to which E. coli Fur
binds. A 160-bp fragment encompassing the promotor region and the putative
iron boxes of the fbpA promoter was incubated with Fur, DNaseI was added,
and the products of these reactions were sequenced to identify nucleotide
peaks that were protected. At 50 nM Fur, a protected region that spanned 33
bp and extended 19 bp upstream and 8 bp downstream of the -35 region of the
fbpA promoter was observed. At higher concentrations of Fur (75 and 100
nM), an extension of this protected region upstream of the -35 region was
observed. Introduction of a plasmid carrying an fbpA-cat transcriptional
fusion in E. coli H1717 (Fur+) resulted in an 88% induction of
chloramphenicol acetyltransferase expression under conditions of iron
restriction; however, chloramphenicol acetyltransferase expression was not
responsive to iron in E. coli H1745 (Fur-), indicating that transcriptional
regulation of fbpA in response to iron occurs via the negative regulator
Fur. The extent of the fbpA operator sequence (42 bp), as defined by our
footprinting analysis, would suggest the binding of two Fur repressor
dimers.
Copyright © 1996, American Society for Microbiology
Analysis of Fur binding to operator sequences within the Neisseria gonorrhoeae fbpA promoter
Department of Microbiology and Immunology, Morehouse School of Medicine, Atlanta, Georgia 30310-1495, USA.
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