Journal of Biological Chemistry
Volume 280, Issue 41, 14 October 2005, Pages 34465-34472
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Enzyme Catalysis and Regulation
Cys-tRNAPro Editing by Haemophilus influenzae YbaK via a Novel Synthetase·YbaK·tRNA Ternary Complex*

https://doi.org/10.1074/jbc.M507550200Get rights and content
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Aminoacyl-tRNA synthetases are multidomain enzymes that often possess two activities to ensure translational accuracy. A synthetic active site catalyzes tRNA aminoacylation, while an editing active site hydrolyzes mischarged tRNAs. Prolyl-tRNA synthetases (ProRS) have been shown to misacylate Cys onto tRNAPro, but lack a Cys-specific editing function. The synthetase-like Haemophilus influenzae YbaK protein was recently shown to hydrolyze misacylated Cys-tRNAPro in trans. However, the mechanism of specific substrate selection by this single domain hydrolase is unknown. Here, we demonstrate that YbaK alone appears to lack specific tRNA recognition capabilities. Moreover, YbaK cannot compete for aminoacyl-tRNAs in the presence of elongation factor Tu, suggesting that YbaK acts before release of the aminoacyl-tRNA from the synthetase. In support of this idea, cross-linking studies reveal the formation of binary (ProRS·YbaK) and ternary (ProRS·YbaK·tRNA) complexes. The binding constants for the interaction between ProRS and YbaK are 550 nm and 45 nm in the absence and presence of tRNAPro, respectively. These results suggest that the specificity of trans-editing by YbaK is ensured through formation of a novel ProRS·YbaK·tRNA complex.

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This work was supported by Grant GM49928 from the National Institutes of Health. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.