The tmRNA website

Abstract
TmRNA (also known as 10Sa RNA) is so-named for itsdual tRNA-like and mRNA-like nature. It is employed ina remarkable trans-translation process to add a Cterminalpeptide tag to the incomplete protein productof a broken mRNA; the tag targets the abnormalprotein for proteolysis. tmRNA sequences have beenidentified in genomes of diverse bacterial phyla,including the most deeply branching. They have alsobeen identified in plastids of the `red" lineage. ThetmRNA Website...