Molecular properties of cytochrome c oxidase in Ascaris respiratory chain and its response to oxygen tension

1.1998年的成果：利用从需氧生长的线虫中分离的线粒体对秀丽隐杆线虫的呼吸链进行了表征。线虫线粒体主要含有泛素-9，红醌-9为次要成分。隐杆线虫线粒体中泛素-9/红醌-9的比值高于猪蛔虫（猪肠道线虫的自由生活阶段）第二阶段幼虫的线粒体。由琥珀酸氧化酶组成的氧化还原酶活性和底物可还原细胞色素的数量与二龄幼虫线粒体的活性相当。秀丽隐杆线虫线粒体富马酸还原酶的比活性低于草隐杆线虫二期幼虫的线粒体，但仍高于哺乳动物的线粒体。这些结果表明，与需氧哺乳动物不同，自由生活的秀丽隐杆线虫能够合成红醌，尽管它的线粒体似乎比草线虫幼虫的线粒体更需氧。1999年成果：鉴定了猪蛔虫幼虫复合体II的Ip亚基，因为Northern杂交表明成虫Ip在幼虫中也有表达。幼虫复合体II的Ip被抗体识别，并通过肽图谱与成体Ip无法区分。deae -纤维素纤维柱层析纯化的幼虫复合体II中Ip的n端42个氨基酸序列与成熟的成虫Ip相同。此外，在PVDF膜上微量分析发现，幼虫的氨基酸组成与成虫的氨基酸组成基本相同。这些结果表明，即使成虫酶作为富马酸还原酶，而幼虫酶作为琥珀酸脱氢酶，这两种不同阶段特异性形式的a . suum复合物II具有共同的Ip亚基。

1.Achievement in l998: The respiratory chain of Caenorhabditis elegans was characterized in mitochondria isolated from aerobically grown nematodes. Nematode mitochondria contain ubiquinone-9 as a major component and rhodoquinone-9 as a minor component. The ratio of ubiquinone-9/rhodoquinone-9 is higher in C. elegans mitochondria than in mitochondria from second-stage larvae of Ascaris suum, the free-living stage of porcine gut-dwelling nematode. The individual oxidoreductase activities comprising succinate-oxidase and the amount of substrate-reducible cytochromes are comparable to those of mitochondria from second-stage larvae of A. suum. The specific activity of fumarate reductase is lower in C. elegans mitochondria than in mitochondria from second-stage larvae of A. suum, but still higher than in mammalian mitochondria. These results indicate that the free-living nematode C. elegans is capable of synthesizing rhodoquinone, as distinguished from aerobic mammalian species, although its mitochondria appear more aerobic than A. suum larval mitochondria.2. Achievement in 1999: The Ip subunit of Ascaris suum larval complex II was characterized because Northern hybridization showed that the adult Ip also is expressed in the larvae. The Ip of larval complex II was recognized by the antibody against adult Ip, and was indistinguishable from the adult Ip by peptide mapping. The N-terminal 42 amino acid sequence of Ip in the larval complex II purified by DEAE-cellulofine column chromatography was identical to that of the mature form of the adult Ip. Furthermore, the amino acid composition of larval Ip determined by micro-analysis on a PVDF membrane is almost the same as that of adult Ip. These results suggest that the two different stage-specific forms of the A. suum complex II share a common Ip subunit, even though the adult enzyme functions as a fumarate reductase, while larval enzyme acts as a succinate dehydrogenase.