Kinetic quality control of anticodon recognition by a eukaryotic aminoacyl-tRNA synthetase.
Aminoacyl-tRNA synthetases are an ancient class of enzymes responsible for the matching of amino acids with anticodon sequences of tRNAs. Eukaryotic tRNA synthetases are often larger than their bacterial counterparts, and several mammalian enzymes use the additional domains to facilitate assembly into a multi-synthetase complex. Human cysteinyl-tRNA synthetase (CysRS) does not associate with the multi-synthetase complex, yet contains a eukaryotic-specific C-terminal extension that follows the tRNA anticodon-binding domain. Here we show by mutational and kinetic analysis that the C-terminal extension of human CysRS is used to selectively improve recognition and binding of the anticodon sequence, such that the specificity of anticodon recognition by human CysRS is higher than that of its bacterial counterparts. However, the improved anticodon recognition is achieved at the expense of a significantly slower rate in the aminoacylation reaction, suggesting a previously unrecognized kinetic quality control mechanism. This kinetic quality control reflects an evolutionary adaptation of some tRNA synthetases to improve the anticodon specificity of tRNA aminoacylation from bacteria to humans, possibly to accommodate concomitant changes in codon usage.
Liu
Cuiping
C
Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Gamper
Howard
H
Shtivelband
Svetlana
S
Hauenstein
Scott
S
Perona
John J
JJ
Hou
Ya-Ming
YM
D000595:Amino Acid Sequence; D000604:Amino Acyl-tRNA Synthetases / Q000737:chemistry* / Q000378:metabolism*; D000926:Anticodon / Q000378:metabolism*; D001483:Base Sequence; D019281:Dimerization; D005057:Eukaryotic Cells / Q000201:enzymology; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012350:RNA, Transfer, Cys / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D046249:Transfer RNA Aminoacylation
D000926:Anticodon; D050505:Mutant Proteins; D012350:RNA, Transfer, Cys; D000604:Amino Acyl-tRNA Synthetases; C019975:cysteinyl-tRNA synthetase