Cytochrome c oxidase of mammals contains a testes-specific isoform of subunit VIb -: the counterpart to testes-specific cytochrome c?
Cytochrome c oxidase of mammals contains a testes-specific isoform of subunit VIb -: the counterpart to testes-specific cytochrome c?
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DOI：
10.1002/mrd.10327
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发表时间：
2003-09-01
影响因子：
2.5
通讯作者：
Grossman, LI
中科院分区：
文献类型：
--
作者：
Hüttemann, M;Jaradat, S;Grossman, LI
精子的运动高度依赖有氧能量代谢，线粒体呼吸链的明显限速步骤是由细胞色素c氧化酶(COX)催化的。COX是唯一显示异构体的电子传递链复合体，这与其被认为的限速作用一致。之前描述了13个亚基中的4个亚基的异构体。我们现在报告的发现是，COX亚单位VIB在人、公牛、大鼠和小鼠中显示出睾丸特异的亚型(COX VIB-2)。对包括卵巢在内的各种大鼠和小鼠组织的分析表明，VIB-2仅在睾丸中表达，而VIB-1转录本在啮齿动物睾丸中缺失，即使在早期发育阶段也是如此。相比之下，这两种异构体都在人类睾丸中转录。与人、大鼠和小鼠睾丸切片的原位杂交显示，VIB-2在所有类型的睾丸细胞中都有转录。在生精小管内，VIB-1在外周的信号强于管腔。此前，细胞色素c是已知的哺乳动物线粒体呼吸链中唯一表达睾丸特异异构体的成分。COX亚基VIB将两个COX单体连接成生理二聚体，是唯一的COX亚基，与细胞色素c一样，仅位于膜间隙。异构体序列之间的显著差异，特别是带电氨基酸的变化，表明与细胞色素c和精子特有的能量需求相互作用。(C)2003年Wiley-Liss，Inc.
Sperm motility is highly dependent on aerobic energy metabolism, of which the apparent rate-limiting step of the mitochondrial respiratory chain is catalyzed by cytochrome c oxidase (COX). COX is the only electron transport chain complex to display isoforms, consistent with its suggested rate-limiting role. Isoforms were previously described for four of the 13 subunits. We now report the discovery that COX subunit VIb displays a testes-specific isoform in human, bull, rat, and mouse (COX VIb-2). Analysis of a variety of rat and mouse tissues, including ovaries, demonstrates exclusive expression of VIb-2 in testes, whereas VIb-1 transcripts are absent in rodent testes, even at early developmental stages. In contrast, both isoforms are transcribed in human testes. In situ hybridizations with human, rat, and mouse testes sections reveal VIb-2 transcripts in all testicular cell types. Within the seminiferous tubules, VIb-1 shows stronger signals in the periphery than in the lumen. Previously, cytochrome c was the only component of the mitochondrial respiratory chain known to express a testes-specific isoform in mammals. COX subunit VIb connects the two COX monomers into the physiological dimeric form, and is the only COX subunit that, like cytochrome c, is solely located in the inter-membrane space. Significant differences between the isoform sequences, in particular changes in charged amino acids, suggest interactions with cytochrome c and sperm-specific energy requirements. (C) 2003 Wiley-Liss, Inc.