Shiba K, Schimmel P, Motegi H, Noda T
Department of Cell Biology, Japanese Foundation for Cancer Research, Tokyo.
J Biol Chem. 1994 Nov 25;269(47):30049-55.
Several class I and class II human tRNA synthetases are clearly related to their bacterial counterparts. We report here the cloning, cDNA sequence, deduced primary structure, and expression in bacteria of a class II human glycyl-tRNA synthetase. While the human sequence aligns well with a Bombyx mori and a Saccharomyces cerevisiae sequence for glycyl-tRNA synthetase, particularly in the region of the class II-defining sequence motifs, it diverges widely from that of the Escherichia coli enzyme. The divergence is so great that from the sequences alone we cannot conclude that the human and E. coli proteins are descended from homologous genes. Moreover, even though the human and E. coli class II alanyl-tRNA synthetases cross-acylate their respective tRNAs, aminoacylations by the recombinant human and E. coli glycyl-tRNA synthetases are restricted to their homologous tRNAs. The species-specific aminoacylations correlate with a nucleotide sequence difference at a location in the acceptor stem that is known to be critical for aminoacylations by the E. coli enzyme. Thus, glycyl-tRNA synthetase may have followed a path of historical development different in at least some respects from that of several other tRNA synthetases.
几种I类和II类人tRNA合成酶与它们的细菌对应物明显相关。我们在此报告II类人甘氨酰-tRNA合成酶的克隆、cDNA序列、推导的一级结构以及在细菌中的表达。虽然人类序列与家蚕和酿酒酵母的甘氨酰-tRNA合成酶序列匹配良好，特别是在II类定义序列基序区域，但它与大肠杆菌酶的序列差异很大。这种差异如此之大，以至于仅从序列我们无法得出人类和大肠杆菌蛋白质来自同源基因的结论。此外，尽管人类和大肠杆菌II类丙氨酰-tRNA合成酶能交叉酰化它们各自的tRNA，但重组的人类和大肠杆菌甘氨酰-tRNA合成酶的氨酰化作用仅限于它们同源的tRNA。物种特异性氨酰化作用与受体茎中一个位置的核苷酸序列差异相关，该位置已知对大肠杆菌酶的氨酰化作用至关重要。因此，甘氨酰-tRNA合成酶可能遵循了一条在至少某些方面与其他几种tRNA合成酶不同的历史发展路径。
