Eubacterial tmRNAs: everywhere except the alpha-Proteobacteria?

Eubacterial tmRNAs mediate, at least in Escherichia coli, recycling of ribo somes stalled at the end of terminatorless mRNAs. A tmRNA-encoded peptide t ag is added to abnormal protein products of truncated mRNAs. This tag is a specific signal for proteolysis of the aberrant protein. To obtain further sequence information, PCR was used to amplify more Eubacterial genes for tm RNA. Fifty-eight new tmDNA sequences including from members of nine additio nal phyla were determined. Remarkably, tmDNA sequences could be amplified f rom all species tested apart from those in the alpha-Proteobacteria, raisin g evolutionary implications. (C) 1999 Elsevier Science B.V. All rights rese rved.