Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois 60115.
Mycologia. 2004 Sep-Oct;96(5):981-9.
The mitochondrial genome of the peronosporomycete water mold Saprolegnia ferax has been characterized as a 46 930 bp circle containing an 8618 bp large inverted repeat (LIR). Eighteen reading frames encode identified subunits of respiratory complexes I, III, IV and V; 16 encode polypeptides of small and large mitoribosome subunits; and one encodes a subunit of the sec-independent protein translocation pathway. Of four additional putative reading frames three are homologues of those found in the related Phytophthora infestans genome. Protein encoding loci in the tightly compacted genome typically are arranged in operon-like clusters including three abutting and two overlapping pairs of reading frames. Translational RNAs include the mitochondrial small and large subunit rRNAs and 25 tRNA species. No tRNAs are encoded to enable translation of any threonine or the arginine CGR codons. The LIR separates the molecule into 19 274 bp large and 10 420 bp small single copy regions, and it encodes intact duplicate copies of four reading frames encoding known proteins, both rRNAs, and five tRNAs. Partial 3' sequences of three additional reading frames are duplicated at single copy sequence junctions. Active recombination between LIR elements generates two distinctive gene orders and uses the duplicated 3' sequences to maintain intact copies of the partially duplicated loci.
水霉目卵菌的线粒体基因组已被鉴定为一个 46930bp 的环状分子，包含一个 8618bp 的大反向重复序列（LIR）。18 个阅读框编码了已鉴定的呼吸复合物 I、III、IV 和 V 的亚基；16 个阅读框编码了小和大亚线粒体核糖体亚基的多肽；一个阅读框编码了 sec 独立蛋白易位途径的亚基。在另外四个假定的阅读框中，有三个与相关的疫霉基因组中的阅读框同源。在紧密压缩的基因组中，蛋白质编码基因座通常以类似于操纵子的簇排列，包括三个相邻和两个重叠的阅读框对。翻译 RNA 包括线粒体小和大亚核糖体 RNA 和 25 种 tRNA 种类。没有编码 tRNA 来翻译任何苏氨酸或精氨酸 CGR 密码子。LIR 将分子分为 19274bp 的大单拷贝区和 10420bp 的小单拷贝区，并编码已知蛋白质的完整重复拷贝的四个阅读框、两个 rRNA 和五个 tRNA。三个额外的阅读框的部分 3'序列在单拷贝序列连接处重复。LIR 元件之间的活性重组产生了两种不同的基因顺序，并使用重复的 3'序列来维持部分重复基因座的完整拷贝。
