Recycling of aborted ribosomal 50S subunit-nascent chain-tRNA complexes by the heat shock protein Hsp15.

Abstract

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.

• Authors: Linhua Jiang, Christiane Schaffitzel, Rouven Bingel-Erlenmeyer, Nenad Ban, Philipp Korber, Roman I Koning, Daniël C de Geus, Jasper R Plaisier, Jan Pieter Abrahams
• Journal: Journal of molecular biology (J Mol Biol) Vol. 386 Issue 5 Pg. 1357-67 (Mar 13 2009) ISSN: 1089-8638 [Electronic] Netherlands
• PMID: 19013177 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• DNA-Binding Proteins
• Escherichia coli Proteins
• Heat-Shock Proteins
• RNA, Bacterial
• hslR protein, E coli
• Puromycin
• RNA, Transfer

Topics

• Cryoelectron Microscopy
• DNA-Binding Proteins (chemistry)
• Escherichia coli Proteins (chemistry)
• Heat-Shock Proteins (chemistry)
• Models, Molecular
• Puromycin (chemistry)
• RNA, Bacterial (chemistry)
• RNA, Transfer (chemistry)
• Ribosome Subunits, Large, Bacterial (chemistry)