Antharavally B S, Poyner R R, Zhang Y, Roberts G P, Ludden P W
Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA.
J Bacteriol. 2001 Oct;183(19):5743-6. doi: 10.1128/JB.183.19.5743-5746.2001.
Site-directed mutagenesis of the draG gene was used to generate altered forms of dinitrogenase reductase-activating glycohydrolase (DRAG) with D123A, H142L, H158N, D243G, and E279R substitutions. The amino acid residues H142 and E279 are not required either for the coordination to the metal center or for catalysis since the variants H142L and E279R retained both catalytic and electron paramagnetic resonance spectral properties similar to those of the wild-type enzyme. Since DRAG-H158N and DRAG-D243G variants lost their ability to bind Mn(II) and to catalyze the hydrolysis of the substrate, H158 and D243 residues could be involved in the coordination of the binuclear Mn(II) center in DRAG.
采用定点诱变draG基因的方法，生成了具有D123A、H142L、H158N、D243G和E279R替换的二氮还原酶激活糖水解酶（DRAG）的变体形式。氨基酸残基H142和E279对于与金属中心的配位或催化作用并非必需，因为变体H142L和E279R保留了与野生型酶相似的催化和电子顺磁共振光谱特性。由于DRAG-H158N和DRAG-D243G变体失去了结合Mn(II)和催化底物水解的能力，H158和D243残基可能参与了DRAG中双核Mn(II)中心的配位。
