Borgford T J, Brand N J, Gray T E, Fersht A R
Biochemistry. 1987 May 5;26(9):2480-6. doi: 10.1021/bi00383a012.
We report the DNA sequence of the valS gene from Bacillus stearothermophilus and the predicted amino acid sequence of the valyl-tRNA synthetase encoded by the gene. The predicted primary structure is for a protein of 880 amino acids with a molecular mass of 102,036. The molecular mass and amino acid composition of the expressed enzyme are in close agreement with those values deduced from the DNA sequence. Comparison of the predicted protein sequence with known protein sequences revealed a considerable homology with the isoleucyl-tRNA synthetase of Escherichia coli. The two enzymes are identical in some 20-25% of their amino acid residues, and the homology is distributed approximately evenly from N-terminus to C-terminus. There are several regions which are highly conservative between the valyl- and isoleucyl-tRNA synthetases. In one of these regions, 15 of 20 amino acids are identical, and in another, 10 of 14 are identical. The valyl-tRNA synthetase also contains a region HLGH (His-Leu-Gly-His) near its N-terminus equivalent to the consensus HIGH (His-Ile-Gly-His) sequence known to participate in the binding of ATP in the tyrosyl-tRNA synthetase. This is the first example of extensive homology found between two different aminoacyl-tRNA synthetases.
我们报道了嗜热脂肪芽孢杆菌valS基因的DNA序列以及该基因编码的缬氨酰-tRNA合成酶的预测氨基酸序列。预测的一级结构是一个由880个氨基酸组成的蛋白质，分子量为102,036。表达酶的分子量和氨基酸组成与从DNA序列推导的值非常一致。将预测的蛋白质序列与已知蛋白质序列进行比较，发现与大肠杆菌的异亮氨酰-tRNA合成酶有相当高的同源性。这两种酶在约20%-25%的氨基酸残基上相同，并且同源性从N端到C端大致均匀分布。缬氨酰-tRNA合成酶和异亮氨酰-tRNA合成酶之间有几个高度保守的区域。在其中一个区域，20个氨基酸中有15个相同，在另一个区域，14个氨基酸中有10个相同。缬氨酰-tRNA合成酶在其N端附近还含有一个HLGH（组氨酸-亮氨酸-甘氨酸-组氨酸）区域，相当于已知参与酪氨酰-tRNA合成酶中ATP结合的共有HIGH（组氨酸-异亮氨酸-甘氨酸-组氨酸）序列。这是在两种不同的氨酰-tRNA合成酶之间发现广泛同源性的第一个例子。
