The ancestral endosymbiosis came with the evolutionary need of an import machinery to address the many nuclear-encoded proteins having functional and regulatory roles in the organelles. We proposed that the protein import machinery could be derived from a bacterial antimicrobial resistance mechanism. We continue our analysis of the determinant of targeting specificity in photosynthetic eukaryotes and complement our exploration of the antimicrobial origin of organelle targeting peptides by analysis of extant model of a pre-endosymbiotic situation. We also retrace the evolutionary history of the translocon machineries.
