Aerobic Repression of the Rhodobacter capsulatus bchCPromoter Involves Cooperative Interactions between CrtJ Bound to Neighboring Palindromes

Abstract

Previous studies demonstrated that bacteriochlorophyll, carotenoid, and light harvesting gene expression in Rhodobacter capsulatus is repressed under aerobic growth conditions by the repressor CrtJ. Isolated CrtJ 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 other the ؊10 -70 recognition sequences. In this study, we demonstrate that CrtJ binds to the two palindromic sites in the bchC promoter in a cooperative manner. The level of cooperativity of CrtJ binding to the ؊35 palindrome was shown to be 26-fold. A distance of 8 base pairs between the two palindromic sites was shown to be critical for cooperative binding, as evidenced by the disruption of binding that resulted when ؉6 and ؉11 base pairs were inserted between the palindromes.

Regulation of Photosynthesis Genes in Rubrivivax gelatinosus : Transcription Factor PpsR Is Involved in both Negative and Positive Control

“…If the cooperative interaction is abolished (ϩ3 or ϩ12 bp between the two consensus sequences), the activation occurs through the interaction between one TyrR dimer and the RNA polymerase (4,12). In addition, Ponnampalam et al have reported that ϩ6 and ϩ11 nucleotide additions between the two consensus sequences abolished CrtJ binding to the bchC promoter, and they suggest that the 8-bp spacing between the two palindrome sites is important for proper cooperative binding of two CrtJ dimers to the promoter (26).…”

“…Nine nucleotides were found in the spacing between the two consensus sequences in the pucBA promoter, while 8 nucleotides were found in the spacing sequence for the crtI promoter. It was reported that both the sequence and the spacing between the two PpsR consensus sequences are important for PpsR/CrtJ binding in Rhodobacter species (26). We assume that R. gelatinosus PpsR behavior (activator-repressor) should be related to the sequence divergences in the PpsRbinding site.…”

“…In fact, repression by CrtJ involves cooperative interactions between two CrtJ molecules bound to adjacent consensus sequences. Mutations in the spacing between the two consensus sequences abolish repression by CrtJ (26).…”

Searching for Palindromic Sequences in Primary Structure of Proteins

“…For example the nuclear glucocorticoid receptor recognizes a palindromic fragment of human DNA [17,18]. Moreover palindromic sequences are present in telomeres and are necessary for initiation of DNA replication therein [19,20], All in all palindromic sequences of DNA were studied in depth and their role is quite well understood [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. On the other hand the presence of palindromic sequences in primary structure of proteins has not gained as much attention [21,22].…”

“…Restriction enzymes which recognize specific sequences of DNA are widely exploited in laboratories for gene isolation and cloning, genetic recombination, examining of chromosome structure, and sequencing of long DNA fragments [1,[7][8][9][10]. Some nuclear receptors recognize as their target palindromic sequences of DNA [11][12][13][14][15][16]. For example the nuclear glucocorticoid receptor recognizes a palindromic fragment of human DNA [17,18].…”