期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 104, 期 27, 页码 11268-11273出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0704769104
关键词
aminoacy-t-RNA synthetase; evolution; pyrrolysine
资金
- NIGMS NIH HHS [GM22854, P01 GM022778, GM22778, R01 GM022854, R37 GM022854] Funding Source: Medline
Pyrrolysine (Pyl), the 22nd natural amino acid and genetically encoded by UAG, becomes attached to its cognate tRNA by pyrrolysyl-tRNA synthetase (PyIRS). We have determined three crystal structures of the Methanosarcina mazei PyIRS complexed with either AMP-PNP, Pyl-AMP plus pyrophosphate, or the Pyl analogue N-epsilon-[(cylopentyloxy)carbonyl]-L-lysine plus ATP. The structures reveal that PyIRS utilizes a deep hydrophobic pocket for recognition of the Pyl side chain. A comparison of these structures with previously determined class 11 tRNA synthetase complexes illustrates that different substrate specificities derive from changes in a small number of residues that form the substrate side-chain-binding pocket. The knowledge of these structures allowed the placement of PyIRS in the aminoacyl-tRNA synthetase (aaRS) tree as the last known synthetase that evolved for genetic code expansion, as well as the finding that Pyl arose before the last universal common ancestral state. The PyIRS structure provides an excellent framework for designing new aaRSs with altered amino acid specificity.
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