Chemical Structure of Posttranslational Modification with A Farnesyl Group on Tryptophan

Abstract

Bacillus subtilis and related bacilli produce a posttranslationally modified oligopeptide, the ComX pheromone, that stimulates natural genetic competence controlled by quorum sensing. The ComX_RO-C-2 pheromone from strain RO-C-2 must be modified with a farnesyl group on the Trp residue, but the precise structure is not known. Here we report the precise nature of posttranslational farnesylation of ComX_RO-C-2 pheromone on the Trp residue, resulting in the formation of a tricyclic structure. The ComX₁₆₈ pheromone, produced by the standard laboratory strain used in the study of B. subtilis, is also posttranslationally farnesylated according to phylogenetic resemblance.