Evolutionary Gain of Alanine Mischarging to Noncognate tRNAs with a G4:U69 Base Pair.
Fidelity of translation, which is predominately dictated by the accuracy of aminoacyl-tRNA synthetases in pairing amino acids with correct tRNAs, is of central importance in biology. Yet, deliberate modifications of translational fidelity can be beneficial. Here we found human and not E. coli AlaRS has an intrinsic capacity for mispairing alanine onto nonalanyl-tRNAs including tRNACys. Consistently, a cysteine-to-alanine substitution was found in a reporter protein expressed in human cells. All human AlaRS-mischarged tRNAs have a G4:U69 base pair in the acceptor stem. The base pair is required for the mischarging. By solving the crystal structure of human AlaRS and comparing it to that of E. coli AlaRS, we identified a key sequence divergence between eukaryotes and bacteria that influences mischarging. Thus, the expanded tRNA specificity of AlaRS appears to be an evolutionary gain-of-function to provide posttranscriptional alanine substitutions in eukaryotic proteins for potential regulations.
Department of Cell and Molecular Biology, The Scripps Research Institute , La Jolla, California 92037, United States.
Litao
L
Sun
Department of Biochemistry and Molecular Biology, University of Chicago , Chicago, Illinois 60637, United States.
Ana Cristina
AC
Gomes
Department of Chemical Physiology, The Scripps Research Institute , La Jolla, California 92037, United States.
Weiwei
W
He
Department of Cell and Molecular Biology, The Scripps Research Institute , La Jolla, California 92037, United States.
Huihao
H
Zhou
Department of Biochemistry and Molecular Biology, University of Chicago , Chicago, Illinois 60637, United States.
Xiaoyun
X
Wang
Department of Biochemistry and Molecular Biology, University of Chicago , Chicago, Illinois 60637, United States.
David W
DW
Pan
Department of Cell and Molecular Biology, The Scripps Research Institute , La Jolla, California 92037, United States.
Paul
P
Schimmel
Department of Biochemistry and Molecular Biology, University of Chicago , Chicago, Illinois 60637, United States.
Tao
T
Pan
Department of Cell and Molecular Biology, The Scripps Research Institute , La Jolla, California 92037, United States.|Department of Chemical Physiology, The Scripps Research Institute , La Jolla, California 92037, United States.
Xiang-Lei
XL
Yang
D000409:Alanine; D000604:Amino Acyl-tRNA Synthetases / Q000737:chemistry / Q000378:metabolism; D020029:Base Pairing; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology; D019143:Evolution, Molecular; D012343:RNA, Transfer / Q000235:genetics* / Q000378:metabolism*
D012343:RNA, Transfer; D000604:Amino Acyl-tRNA Synthetases; D000409:Alanine