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Published December 18, 2009 | Accepted Version
Journal Article Open

Switching from an Induced-Fit to a Lock-and-Key Mechanism in an Aminoacyl-tRNA Synthetase with Modified Specificity

Abstract

Methionyl-tRNA synthetase (MetRS) specifically binds its methionine substrate in an induced-fit mechanism, with methionine binding causing large rearrangements. Mutated MetRS able to efficiently aminoacylate the methionine (Met) analog azidonorleucine (Anl) have been identified by saturation mutagenesis combined with in vivo screening procedures. Here, the crystal structure of such a mutated MetRS was determined in the apo form as well as complexed with Met or Anl (1.4 to 1.7 Å resolution) to reveal the structural basis for the altered specificity. The mutations result in both the loss of important contacts with Met and the creation of new contacts with Anl, thereby explaining the specificity shift. Surprisingly, the conformation induced by Met binding in wild-type MetRS already occurs in the apo form of the mutant enzyme. Therefore, the mutations cause the enzyme to switch from an induced-fit mechanism to a lock-and-key one, thereby enhancing its catalytic efficiency.

Additional Information

© 2009 Elsevier Ltd. Received 24 July 2009; revised 8 October 2009; accepted 9 October 2009. Edited by J. Doudna. Available online 16 October 2009. We acknowledge the ESRF for providing the X-ray facilities on beamline ID14-2 as well as the synchrotron SOLEIL for providing the X-ray facilities on beamline Proxima I. We thank Centre National de la Recherche Scientifique and Ecole Polytechnique for financial support to the "Unité Mixte de Recherche 7654". Work at Caltech was supported by National Institutes of Health Grant GM62523 and by the Army Research Office through the Institute for Collaborative Biotechnologies.

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Created:
August 21, 2023
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October 19, 2023