A MUTANT T4 LYSOZYME DISPLAYS 5 DIFFERENT CRYSTAL CONFORMATIONS
A MUTANT T4 LYSOZYME DISPLAYS 5 DIFFERENT CRYSTAL CONFORMATIONS
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DOI：
10.1038/348263a0
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发表时间：
1990-11-15
期刊：
影响因子：
64.8
通讯作者：
MATTHEWS, BW
中科院分区：
文献类型：
--
作者：
FABER, HR;MATTHEWS, BW
噬菌体 T4 溶菌酶由两个结构域组成，两个结构域之间形成酶的活性位点裂缝 1,2。晶体学测定的蛋白质2热位移参数表明，两个结构域的氨基末端围绕穿过分子腰部的轴经历“铰链弯曲”运动。这种构象迁移率对于允许底物进入酶的活性位点可能很重要。我们在此报告了突变型 T4 溶菌酶的晶体学研究，进一步证明了该蛋白质的构象灵活性。该酶的突变体形式的蛋氨酸残基（Met 6）被异亮氨酸取代，在晶格中结晶出四个独立的分子。这四种分子具有明显不同的构象。突变蛋白也可以以标准形式结晶，其结构与野生型蛋白非常相似。因此突变蛋白可以采用五种不同的晶体构象。 T4溶菌酶两个结构域交叉点处的异亮氨酸取代甲硫氨酸明显增强了推测在野生型蛋白质中发生的铰链弯曲运动，而不会显着影响蛋白质的催化活性或热稳定性。
PHAGE T4 lysozyme consists of two domains between which is formed the active-site cleft of the enzyme1,2. The crystallographically determined thermal displacement parameters for the protein2suggested that the amino terminal of the two domains undergoes 'hinge-bending' motion about an axis passing through the waist of the molecule. Such conformational mobility may be important in allowing access of substrates to the active site of the enzyme1. We report here a crystallographic study of a mutant T4 lysozyme which demonstrates further the conformational flexibility of the protein. A mutant form of the enzyme with a methionine residue (Met 6) replaced by isoleucine crystallizes with four independent molecules in the crystal lattice. These four molecules have distinctly different conformations. The mutant protein can also crystallize in standard form with a structure very similar to the wild-type protein. Thus the mutant protein can adopt five different crystal conformations. The isoleucine for methionine substitution at the intersection of the two domains of T4 lysozyme apparently enhances the hinge-bending motion presumed to occur in the wild-type protein, without significantly affecting the catalytic activity or thermal stability of the protein.