A mitochondrial cytochrome b mutation causing severe respiratory chain enzyme deficiency in humans and yeast
A mitochondrial cytochrome b mutation causing severe respiratory chain enzyme deficiency in humans and yeast
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DOI：
10.1111/j.1742-4658.2005.04779.x
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发表时间：
2005-07-01
期刊：
影响因子：
5.4
通讯作者：
Taylor, RW
中科院分区：
文献类型：
--
作者：
Blakely, EL;Mitchell, AL;Taylor, RW
虽然大多数疾病相关的线粒体DNA突变表现出显着的生化和临床异质性，突变内的神经编码的人细胞色素B基因（MTCY B）几乎完全与孤立的肌肉中的复合物III缺乏症和涉及运动不耐受的临床表现。最近的研究表明，少数MTCYB突变与涉及复合物I和III的组合酶复合物缺陷相关，这是由于缺乏组装的复合物III导致复合物I的急剧损失，证实了这两种复合物之间的结构依赖性。我们提出了一个病人的生化和分子遗传学研究与肌肉和大脑的参与和严重减少的活动，这两个复合物I和III在骨骼肌由于一个新的突变MTCYB基因，预测取代（Arg 318 Pro）的一个高度保守的氨基酸。与戏剧性的生物化学缺陷，蛋白质印迹和BN-PAGE实验表明组装复合物I和III亚基的损失。在酵母酶中的等效氨基酸取代（Lys 319 Pro）的生物化学研究表明，酶活性的损失和bc（1）复合物的稳定状态水平的降低，在突变确认致病性。
Whereas the majority of disease-related mitochondrial DNA mutations exhibit significant biochemical and clinical heterogeneity, mutations within the mitochondrially encoded human cytochrome b gene (MTCYB) are almost exclusively associated with isolated complex III deficiency in muscle and a clinical presentation involving exercise intolerance. Recent studies have shown that a small number of MTCYB mutations are associated with a combined enzyme complex defect involving both complexes I and III, on account of the fact that an absence of assembled complex III results in a dramatic loss of complex I, confirming a structural dependence between these two complexes. We present the biochemical and molecular genetic studies of a patient with both muscle and brain involvement and a severe reduction in the activities of both complexes I and III in skeletal muscle due to a novel mutation in the MTCYB gene that predicts the substitution (Arg318Pro) of a highly conserved amino acid. Consistent with the dramatic biochemical defect, Western blotting and BN-PAGE experiments demonstrated loss of assembled complex I and III subunits. Biochemical studies of the equivalent amino-acid substitution (Lys319Pro) in the yeast enzyme showed a loss of enzyme activity and decrease in the steady-state level of bc(1) complex in the mutant confirming pathogenicity.