Evolutionary gain of highly divergent tRNA specificities by two isoforms of human histidyl-tRNA synthetase.
The discriminator base N73 is a key identity element of tRNAHis. In eukaryotes, N73 is an "A" in cytoplasmic tRNAHisand a "C" in mitochondrial tRNAHis. We present evidence herein that yeast histidyl-tRNA synthetase (HisRS) recognizes both A73 and C73, but somewhat prefers A73 even within the context of mitochondrial tRNAHis. In contrast, humans possess two distinct yet closely related HisRS homologues, with one encoding the cytoplasmic form (with an extra N-terminal WHEP domain) and the other encoding its mitochondrial counterpart (with an extra N-terminal mitochondrial targeting signal). Despite these two isoforms sharing high sequence similarities (81% identity), they strongly preferred different discriminator bases (A73 or C73). Moreover, only the mitochondrial form recognized the anticodon as a strong identity element. Most intriguingly, swapping the discriminator base between the cytoplasmic and mitochondrial tRNAHisisoacceptors conveniently switched their enzyme preferences. Similarly, swapping seven residues in the active site between the two isoforms readily switched their N73 preferences. This study suggests that the human HisRS genes, while descending from a common ancestor with dual function for both types of tRNAHis, have acquired highly specialized tRNA recognition properties through evolution.
Department of Life Sciences, National Central University, Jungli District, Taoyuan, 32001, Taiwan.
Yi-Hsueh
YH
Lee
Department of Life Sciences, National Central University, Jungli District, Taoyuan, 32001, Taiwan.
Chia-Pei
CP
Chang
Department of Life Sciences, National Central University, Jungli District, Taoyuan, 32001, Taiwan.
Yu-Ju
YJ
Cheng
Department of Life Sciences, National Central University, Jungli District, Taoyuan, 32001, Taiwan.
Yi-Yi
YY
Kuo
Institute of Bioinformatics and Systems Biology, National Chiao Tung University, Hsinchu, 30068, Taiwan.
Yeong-Shin
YS
Lin
Department of Life Sciences, National Central University, Jungli District, Taoyuan, 32001, Taiwan. dukewang@cc.ncu.edu.tw.
Chien-Chia
CC
Wang
D000595:Amino Acid Sequence; D049148:Aminoacylation; D001412:Bacillus subtilis / Q000201:enzymology; D004926:Escherichia coli / Q000201:enzymology; D019143:Evolution, Molecular; D006643:Histidine-tRNA Ligase / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D050505:Mutant Proteins / Q000378:metabolism; D010802:Phylogeny; D012343:RNA, Transfer / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D013379:Substrate Specificity
D007527:Isoenzymes; D050505:Mutant Proteins; D012343:RNA, Transfer; D006643:Histidine-tRNA Ligase
Aminoacyl-tRNA synthetase; Evolution; Phylogenetic analysis; Protein synthesis; Subfunctionalization; tRNA