Posttranslational isoprenylation of a tryptophan residue identified from Bacillus quorum sensing pheromone, ComX pheromone, is unique and essential for the bioactivity. A modifying enzyme, ComQ, forms ComX pheromone from the ComX precursor and isoprenyl pyrophosphate and exhibits moderate similarity to isoprenyl pyrophosphate synthases. We investigated non-conserved region in ComQ, corresponding to isopentenyl pyrophosphate binding region of the synthases, using in vitro cell-free isoprenylation. These results suggested that the only conserved aspartic acid residue in the region of ComQ is critical for enzyme activity and responsible for ComX binding. Our findings should contribute to basic understanding of the mechanism of tryptophan isoprenylation.
Keywords: Bacillus subtilis; isoprenylation; posttranslational modification; quorum sensing; tryptophan.