Willison J C, Härtlein M, Leberman R
European Molecular Biology Laboratory, Grenoble Outstation, France.
J Bacteriol. 1995 Jun;177(11):3347-50. doi: 10.1128/jb.177.11.3347-3350.1995.
A mutant of Escherichia coli resistant to serine hydroxamate which has a large increase in Km for serine of seryl-tRNA synthetase is described. The mutant serS gene was cloned and sequenced and was found to contain a single-base-pair mutation, resulting in the substitution of the residue alanine 262 by valine in motif 2. The methyl side chain of alanine 262 is not exposed at the active site, and molecular modeling indicated that replacement of alanine 262 by valine does not significantly affect the configuration of amino acids at the active site. This finding suggests that the residue at this position may be involved in a conformational change (possibly induced by ATP binding) which is necessary for optimal binding of the cognate amino acid.
描述了一种对丝氨酸异羟肟酸具有抗性的大肠杆菌突变体，该突变体的丝氨酰 - tRNA合成酶对丝氨酸的Km值大幅增加。对该突变体的serS基因进行了克隆和测序，发现其含有一个单碱基对突变，导致基序2中的第262位残基丙氨酸被缬氨酸取代。丙氨酸262的甲基侧链在活性位点不暴露，分子模拟表明丙氨酸262被缬氨酸取代不会显著影响活性位点氨基酸的构象。这一发现表明该位置的残基可能参与了一种构象变化（可能由ATP结合诱导），而这种构象变化对于同源氨基酸的最佳结合是必需的。
