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Defects in Transient tRNA Translocation Bypass tRNA Synthetase Quality Control Mechanisms*

By Rachel A. Hellmann and Susan A. Martinis

Abstract

Quality control mechanisms during protein synthesis are essential to fidelity and cell survival. Leucyl-tRNA synthetase (LeuRS) misactivates non-leucine amino acids including isoleucine, methionine, and norvaline. To prevent translational errors, mischarged tRNA products are translocated 30Å from the canonical aminoacylation core to a hydrolytic editing-active site within a completely separate domain. Because it is transient, the tRNA translocation mechanism has been difficult to isolate. We have identified a “translocation peptide” within Escherichia coli LeuRS. Mutations in the translocation peptide cause tRNA to selectively bypass the editing-active site, resulting in mischarging that is lethal to the cell. This bypass mechanism also rescues aminoacylation of an editing site mutation that hydrolyzes correctly charged Leu-tRNALeu. Thus, these LeuRS mutants charge tRNALeu but fail to translocate these products to the hydrolytic site, where they are cleared to guard against genetic code ambiguities

Topics: Protein Synthesis, Post-Translational Modification, and Degradation
Publisher: American Society for Biochemistry and Molecular Biology
OAI identifier: oai:pubmedcentral.nih.gov:2670153
Provided by: PubMed Central
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