Petruzzella V, Vergari R, Puzziferri I, Boffoli D, Lamantea E, Zeviani M, Papa S
Department of Medical Biochemistry and Biology, University of Bari, Piazza G. Cesare, 70124 Bari, Italy.
Hum Mol Genet. 2001 Mar 1;10(5):529-35. doi: 10.1093/hmg/10.5.529.
Sequence analysis of mitochondrial and nuclear candidate genes of complex I in children with deficiency of this complex and exhibiting Leigh-like syndrome has revealed, in one of them, a novel mutation in the NDUFS4 gene encoding the 18 kDa subunit. Phosphorylation of this subunit by cAMP-dependent protein kinase has previously been found to activate the complex. The present mutation consists of a homozygous G-->A transition at nucleotide position +44 of the coding sequence of the gene, resulting in the change of a tryptophan codon to a stop codon. Such mutation causes premature termination of the protein after only 14 amino acids of the putative mitochondrial targeting peptide. Fibroblast cultures from the patient exhibited severe reduction of the rotenone-sensitive NADH-->UQ oxidoreductase activity of complex I, which was insensitive to cAMP stimulation. Two-dimensional electrophoresis showed the absence of detectable normally assembled complex I in the inner mitochondrial membrane. These findings show that the expression of the NDUFS4 gene is essential for the assembly of a functional complex I.
对患有该复合体缺乏症并表现出类Leigh综合征的儿童的线粒体和细胞核中复合体I候选基因进行序列分析，结果显示，其中一名儿童的编码18 kDa亚基的NDUFS4基因存在一种新的突变。此前发现，该亚基被cAMP依赖性蛋白激酶磷酸化后会激活该复合体。目前的突变是基因编码序列核苷酸位置+44处的纯合G→A转换，导致色氨酸密码子变为终止密码子。这种突变导致在仅经过假定的线粒体靶向肽的14个氨基酸后蛋白质就提前终止。患者的成纤维细胞培养物显示复合体I对鱼藤酮敏感的NADH→UQ氧化还原酶活性严重降低，且对cAMP刺激不敏感。二维电泳显示线粒体内膜中不存在可检测到的正常组装的复合体I。这些发现表明，NDUFS4基因的表达对于功能性复合体I的组装至关重要。
