Jk. Lee et al., TRANSCRIPTIONAL REGULATION OF PUC OPERON EXPRESSION IN RHODOBACTER-SPHAEROIDES - INVOLVEMENT OF AN INTEGRATION HOST FACTOR-BINDING SEQUENCE, The Journal of biological chemistry, 268(32), 1993, pp. 24491-24497
The putative overlapping consensus sequences (-129 to -105) for bindin
g of fumarate nitrate reductase regulator- and integration host factor
(IHF)-like proteins to puc operon upstream DNA of Rhodobacter sphaero
ides was protected from DNase I digestion by purified Escherichia coli
IHF. The binding of E. coli IHF to the purported IHF-binding site in
the puc upstream DNA is highly sequence-specific. The recorded binding
affinity was significantly lower than that of E. coli IHF to the lamb
da attP site. Employing site-directed changes in the DNA sequence with
in the -129 to -105 region, a loss in IHF binding, as monitored throug
h gel retardation analysis, was correlated with alterations in puc ope
ron expression monitored through the use of puc=lacZ transcriptional f
usions. These results suggest that the IHF-binding site is involved in
repression of puc operon transcription by oxygen as well as modulatio
n of puc operon transcription levels by incident light intensity. Muta
tions specific to the upstream half of the putative fumarate nitrate r
eductase regulator-binding site of the puc upstream DNA did not show a
ny physiological effects under the experimental conditions employed. T
aken together, these studies reveal that the DNA sequence between -129
to -105 may involve facilitation of the interaction between upstream
and downstream cis-acting regulatory sequences involved in puc operon
expression.