Evolutionary adaptation of bacterial proteomes to translation-impeding sequences

Microbial translation arrest peptides monitor intracellular environments and feedback-regulate downstream gene expression. Previous studies have identified a class of bacterial arrest peptides with C-terminal RAPP-like sequences, encoded upstream of genes involved in protein localization. In this study, we found that among RAPP-like sequences, RAPP (Arg-Ala-Pro-Pro) and RGPP (Arg-Gly-Pro-Pro) could more readily evolve into translation-impeding sequences with a particularly robust arrest that is refractory to EF-P. RAPP-like motifs were found to be strongly excluded from bacterial proteomes, likely reflecting the risk of disrupting the cellular translation system. Meanwhile, these motifs tended to occur near the C-terminus of relatively small secretory and membrane proteins. Notably, they were encoded upstream of genes with diverse functions beyond protein localization. Indeed, we identified seven RAPP/RGPP-containing arrest peptides from Streptomyces lividans encoded upstream of genes with diverse functions. These findings illustrate the bidirectional evolution of RAPP-containing proteins: their elimination from bacterial proteomes and their adaptation into arrest peptides with various regulatory roles.