van der Giezen M, Rechinger K B, Svendsen I, Durand R, Hirt R P, Fèvre M, Embley T M, Prins R A
University of Groningen, Department of Microbiology, Haren, The Netherlands.
Mol Microbiol. 1997 Jan;23(1):11-21. doi: 10.1046/j.1365-2958.1997.1891553.x.
The hydrogenosomal malic enzyme (ME) was purified from the anaerobic fungus Neocallimastix frontalis. Using reverse genetics, the corresponding cDNA was isolated and characterized. The deduced amino acid sequence of the ME showed high similarity to ME from metazoa, plants and protists. Putative functional domains for malate and NAD+/NADP+ binding were identified. Phylogenetic analysis of the deduced amino acid sequence of the new ME suggests that it is homologous to reference bacterial and eukaryotic ME. Most interestingly, the cDNA codes for a protein which contains a 27-amino-acid N-terminus which is not present on the purified mature protein. This presequence shares features with known mitochondrial targeting signals, including an enrichment in Ala, Leu, Ser, and Arg, and the presence of an Arg at position-2 relative to amino acid 1 of the mature protein. This is the first report of a mitochondrial-like targeting signal on a hydrogenosomal enzyme from an anaerobic fungus and provides support for the hypothesis that hydrogenosomes in Neocallimastix frontalis might be modified mitochondria.
从厌氧真菌新丽鞭毛虫（Neocallimastix frontalis）中纯化出了氢化酶体苹果酸酶（ME）。利用反向遗传学方法，分离并鉴定了相应的cDNA。推导的ME氨基酸序列与后生动物、植物和原生生物的ME具有高度相似性。确定了苹果酸和NAD+/NADP+结合的推定功能域。对新ME推导氨基酸序列的系统发育分析表明，它与参考细菌和真核生物的ME同源。最有趣的是，该cDNA编码的蛋白质含有一个27个氨基酸的N端，而纯化的成熟蛋白质上不存在该N端。该前序列与已知的线粒体靶向信号具有共同特征，包括Ala、Leu、Ser和Arg的富集，以及相对于成熟蛋白质氨基酸1的第2位存在Arg。这是关于厌氧真菌氢化酶体酶上类似线粒体靶向信号的首次报道，并为新丽鞭毛虫中的氢化酶体可能是修饰的线粒体这一假说提供了支持。
