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

JOURNAL OF MOLECULAR BIOLOGY

卷:394

Article

Schmitt, Emmanuelle¹  Tanrikulu, I. Caglar²  Yoo, Tae Hyeon²  Panvert, Michel¹  Tirrell, David A.²  Mechulam, Yves¹ 

[1] Ecole Polytech, Biochim Lab, CNRS, UMR7654, F-91128 Palaiseau, France

[2] CALTECH, Div Chem & Chem Engn, Pasadena, CA 91125 USA

关键词: aminoacyl-tRNA synthetase;    methionine;    azidonorleucine;    induced fit;    X-ray crystallography;   

DOI  :  10.1016/j.jmb.2009.10.016

来源: Elsevier

【 摘 要 】

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 angstrom 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. (C) 2009 Elsevier Ltd. All rights reserved.

【 授权许可】

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