3bbu

Publication Abstract from PubMed

When heat shock prematurely dissociates a translating bacterial ribosome, its 50S subunit is prevented from reinitiating protein synthesis by tRNA covalently linked to the unfinished protein chain that remains threaded through the exit tunnel. Hsp15, a highly upregulated bacterial heat shock protein, reactivates such dead-end complexes. Here, we show with cryo-electron microscopy reconstructions and functional assays that Hsp15 translocates the tRNA moiety from the A site to the P site of stalled 50S subunits. By stabilizing the tRNA in the P site, Hsp15 indirectly frees up the A site, allowing a release factor to land there and cleave off the tRNA. Such a release factor must be stop codon independent, suggesting a possible role for a poorly characterized class of putative release factors that are upregulated by cellular stress, lack a codon recognition domain and are conserved in eukaryotes.

Recycling of aborted ribosomal 50S subunit-nascent chain-tRNA complexes by the heat shock protein Hsp15.,Jiang L, Schaffitzel C, Bingel-Erlenmeyer R, Ban N, Korber P, Koning RI, de Geus DC, Plaisier JR, Abrahams JP J Mol Biol. 2009 Mar 13;386(5):1357-67. Epub 2008 Nov 5. PMID:19013177^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.