Streptomyces coelicolor SsrA When translating ribosomes become stalled on bacterial mRNAs, the SsrA RNA, which acts as both a tRNA and mRNA, contributes a non-coded residue to the nascent polypeptide and then serves as a message for the translation of a short C-terminal polypeptide. SsrA-tagged proteins are degraded by ATP-dependent proteases related to Hsp104. Streptomyces is a gram-positive bacterium found in soil that produces first vegetative mycelia that penetrate the growth substrate and later aerial mycelia that give rise to light coloured or white spores. This simple developmental cycle is controlled in part by the efficiency of translation of open reading frames containing rarely used codons. We are using Streptomyces to study the role of ribosome recycling, SsrA tagging and protein degradation in development.
