Kim Hakjung
Department of Chemistry, College of Natural Science, Daegu University, Kyoungsan 712-714, Korea.
J Biochem Mol Biol. 2002 Jul 31;35(4):437-41. doi: 10.5483/bmbrep.2002.35.4.437.
Dihydrolipoamide dehydrogenase (E3) is a member of the pyridine nucleotide-disulfide oxidoreductase family. Thr residues are highly conserved. They are at the active site disulfide-bond regions of most E3s and other oxidoreductases. The crystal structure of Azotobacter vinelandii E3 suggests that the hydroxyl group of Thr that are involved in the FAD binding interact with the adenosine phosphate of FAD. However, several prokaryotic E3s have Val instead of Thr. To investigate the meaning and importance of the Thr conservation in many E3s, the corresponding residue, Thr-44, in human E3 was substituted to Val by site-directed mutagenesis. The mutant's E3 activity showed about a 2.2-fold decrease. Its UV-visible and fluorescence spectra indicated that the mutant might have a slightly different microenvironment at the FAD-binding region.
二氢硫辛酰胺脱氢酶(E3)是吡啶核苷酸 - 二硫化物氧化还原酶家族的成员。苏氨酸(Thr)残基高度保守。它们位于大多数E3和其他氧化还原酶的活性位点二硫键区域。棕色固氮菌E3的晶体结构表明,参与黄素腺嘌呤二核苷酸(FAD)结合的苏氨酸的羟基与FAD的磷酸腺苷相互作用。然而,几种原核生物E3含有缬氨酸(Val)而非苏氨酸。为了研究许多E3中苏氨酸保守性的意义和重要性,通过定点诱变将人E3中相应的残基苏氨酸 - 44替换为缬氨酸。突变体的E3活性显示出约2.2倍的下降。其紫外可见光谱和荧光光谱表明,突变体在FAD结合区域可能具有略有不同的微环境。