Fourmy D, Mechulam Y, Brunie S, Blanquet S, Fayat G
Laboratoire de Biochimie, Unité de Recherche Associée 240 du Centre National de la Recherche Scientifique, Ecole Polytechnique, Palaiseau, France.
FEBS Lett. 1991 Nov 4;292(1-2):259-63. doi: 10.1016/0014-5793(91)80879-8.
Comparison of the amino-acid sequences of several methionyl-tRNA synthetases indicates the occurrence of a few conserved motifs, having a possible functional significance. The role of one of these motifs, centered at position 300 in the E. coli enzyme sequence, was assayed by the use of site-directed mutagenesis. Substitution of the His301 or Trp305 residues by Ala resulted in a large decrease in methionine affinity, whereas the change of Val298 into Ala had only a moderate effect. The catalytic rate of the enzyme was unimpaired by these substitutions. It is concluded that the above conserved amino-acid region is located at or close to the amino-acid binding pocket of methionyl-tRNA synthetase.
几种甲硫氨酰 - tRNA合成酶的氨基酸序列比较表明存在一些保守基序，这些基序可能具有功能意义。通过定点诱变分析了这些基序之一的作用，该基序以大肠杆菌酶序列中的第300位为中心。将His301或Trp305残基替换为丙氨酸会导致甲硫氨酸亲和力大幅下降，而将Val298替换为丙氨酸只有中等程度的影响。这些替换并未损害该酶的催化速率。得出的结论是，上述保守氨基酸区域位于甲硫氨酰 - tRNA合成酶的氨基酸结合口袋处或附近。
