ComEB protein is dispensable for the transformation but must be translated for the optimal synthesis of comEC

Abstract

We show that the ComEB protein is not required for transformation in Bacillus subtilis, despite its expression from within the comE operon under competence control, nor is it required for the correct polar localization of ComGA. We show further that the synthesis of the putative channel protein ComEC is translationally coupled to the upstream comEB open reading frame, so that the translation of comEB and a suboptimal ribosomal‐binding site embedded in its sequence are needed for proper comEC expression. Translational coupling appears to be a common mechanism in three major competence operons for the adjustment of protein amounts independent of transcriptional control, probably ensuring the correct stoichiometries for assembly of the transformation machinery. comEB and comFC, respectively, encode cytidine deaminase and a protein resembling type 1 phosphoribosyl transferases and we speculate that nucleotide scavenging proteins are produced under competence control for efficient reutilization of the products of degradation of the non‐transforming strand during DNA uptake.

ComF is a key mediator in single-stranded DNA transport and handling during natural transformation

“…6b and Supplementary Table 1), can still partially rescue the transformation phenotype of a DcomF mutant (Figure 1b), suggesting that nucleotide binding to ComF could provide a fine-tuning mechanism of the transformation process. Such a scenario would be consistent with the recently proposed hypothesis that ComF provides a link between transformation and metabolism 48 .…”