Binding Site of Restriction-modification System Controller Protein in Mollicutes

Background: Bacteria of the class Mollicutes underwent extreme reduction of genomes and gene expression control systems. Only a few regulators are known to date. In this work, we describe a novel group of transcriptional regulators that are distributed within different Mollicutes and control the expression of restriction-modification systems (RM-systems).

Results: We performed cross-species search of putative regulators of RM-systems (C-proteins) and respective binding sites in Mollicutes. We identified a set of novel putative C-protein binding motifs distributed within Mollicutes. We studied the most frequent motif and respective C-protein on the model of Mycoplasma gallisepticum S6. We confirmed our prediction and identified key nucleotides important for C-protein binding. Further we identified novel target promoters of C-protein in M. gallisepticum.

Conclusions: We found that C-protein of M. gallisepticum binds predicted conserved direct repeats of the (GTGTTAN) motif. Apart from its own operon promoter, HsdC can bind to the promoters of the clpB chaperone gene and a tRNA cluster.