A common evolutionary origin for mitochondria and hydrogenosomes
A common evolutionary origin for mitochondria and hydrogenosomes
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DOI：
10.1073/pnas.93.18.9651
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发表时间：
1996-09-03
影响因子：
11.1
通讯作者：
Johnson, PJ
中科院分区：
文献类型：
--
作者：
Bui, ETN;Bradley, PJ;Johnson, PJ
滴虫是最早脱离真核血统主线的真核生物之一。与它们古老的性质保持一致，这些兼性厌氧原生生物缺乏大多数真核生物中发现的两种“标志”细胞器：线粒体和过氧化物酶体。然而，毛滴虫确实含有一种参与碳水化合物代谢的不寻常细胞器，称为氢糖体。与线粒体一样，氢酶体是双膜限制的细胞器，使用丙酮酸作为主要底物产生 ATP。然而，氢酶体与线粒体明显不同，因为它们缺乏 DNA、细胞色素和柠檬酸循环，相反，它们含有厌氧细菌中常见的酶，并且能够产生分子氢。我们在此表明，氢糖体含有热休克蛋白、Hsp70、Hsp60 和 Hsp10，其特征序列仅在线粒体和 α-革兰氏阴性紫色细菌 Hsp 中保守。氢糖体 Hsp60 的生化分析表明，从细胞器中分离的成熟蛋白缺乏短的 N 端序列，与大多数核编码线粒体基质蛋白所观察到的相似。此外，氢糖体 Hsp60 的系统发育分析Hsp70、Hsp60 和 Hsp10 显示这些蛋白质在仅由线粒体同源物组成的单系群中分支。这些数据证实线粒体和氢糖体具有共同的真细菌祖先，并暗示最早分支的真核生物含有在高等真核生物中产生线粒体的内共生体。
Trichomonads are among the earliest eukaryotes to diverge from the main line of eukaryotic descent, Keeping with their ancient nature, these facultative anaerobic protists lack two ''hallmark'' organelles found in most eukaryotes: mitochondria and peroxisomes. Trichomonads do, however, contain an unusual organelle involved in carbohydrate metabolism called the hydrogenosome. Like mitochondria, hydrogenosomes are double-membrane bounded organelles that produce ATP using pyruvate as the primary substrate. Hydrogenosomes are, however, markedly different from mitochondria as they lack DNA, cytochromes and the citric acid cycle, Instead, they contain enzymes typically found in anaerobic bacteria and are capable of producing molecular hydrogen. We show here that hydrogenosomes contain heat shock proteins, Hsp70, Hsp60, and Hsp10, with signature sequences that are conserved only in mitochondrial and alpha-Gram-negative purple bacterial Hsps, Biochemical analysis of hydrogenosomal Hsp60 shows that the mature protein isolated from the organelle lacks a short, N-terminal sequence, similar to that observed for most nuclear-encoded mitochondrial matrix proteins, Moreover, phylogenetic analyses of hydrogenosomal Hsp70, Hsp60, and Hsp10 show that these proteins branch within a monophyletic group composed exclusively of mitochondrial homologues. These data establish that mitochondria and hydrogenosomes have a common eubacterial ancestor and imply that the earliest-branching eukaryotes contained the endosymbiont that gave rise to mitochondria in higher eukaryotes.