Videira A, Azevedo J E, Werner S, Cabral P
Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Portugal.
Biochem J. 1993 May 1;291 ( Pt 3)(Pt 3):729-32. doi: 10.1042/bj2910729.
The 12.3 kDa subunit of complex I (respiratory-chain NADH dehydrogenase) is a nuclear-coded protein of the hydrophobic fragment of the enzyme. We have isolated and sequenced a full-length cDNA clone coding for this polypeptide. The deduced protein is 104 amino acid residues long with a molecular mass of 12305 Da. This particular subunit of complex I lacks a cleavable mitochondrial targeting sequence. In agreement with its localization within complex I, we have found that this subunit behaves like an intrinsic membrane protein. Nevertheless, the deduced protein is rather hydrophilic, exhibiting no hydrophobic domain long enough to traverse a membrane in an alpha-helical conformation. The 12.3 kDa subunit shows a significant similarity to the hinge protein of complex III, suggesting that these two polypeptides may be involved in identical functions. This complex I subunit is coded for by a single gene. Applying restriction-fragment-length-polymorphism mapping, we located the gene on the right side of the centromere in linkage group I, linked to the lys-4 locus.
复合体I（呼吸链NADH脱氢酶）的12.3 kDa亚基是该酶疏水片段的一种核编码蛋白。我们已分离并测序了编码此多肽的全长cDNA克隆。推导的蛋白质由104个氨基酸残基组成，分子量为12305 Da。复合体I的这一特定亚基缺乏可切割的线粒体靶向序列。与其在复合体I中的定位一致，我们发现该亚基表现得像一种内在膜蛋白。然而，推导的蛋白质相当亲水，没有足够长的疏水结构域以α螺旋构象穿过膜。12.3 kDa亚基与复合体III的铰链蛋白显示出显著相似性，表明这两种多肽可能参与相同的功能。这个复合体I亚基由单个基因编码。应用限制性片段长度多态性图谱分析，我们将该基因定位在连锁群I着丝粒右侧，与lys-4位点连锁。
