Sn. Ponnampalam et al., AEROBIC REPRESSION OF THE RHODOBACTER-CAPSULATUS BCHC PROMOTER INVOLVES COOPERATIVE INTERACTIONS BETWEEN CRTJ BOUND TO NEIGHBORING PALINDROMES, The Journal of biological chemistry, 273(46), 1998, pp. 30757-30761
Previous studies demonstrated that bacteriochlorophyll, carotenoid, an
d light harvesting gene expression in Rhodobacter capsulatus is repres
sed under aerobic growth conditions by the repressor CrtJ. Isolated Cr
tJ is known to bind to the palindrome TGTN(12)ACA, which is present in
two copies in the bchC promoter, one of which spans the -35 and the o
ther the -10 sigma-70 recognition sequences. In this study, we demonst
rate that CrtJ binds to the two palindromic sites in the bchC promoter
in a cooperative manner. The level of cooperativity of CrtJ binding t
o the -35 palindrome was shown to be 26-fold. A distance of 8 base pai
rs between the two palindromic sites was shown to be critical for coop
erative binding, as evidenced by the disruption of binding that result
ed when +6 and +11 base pairs were inserted between the palindromes.