Park Ae Kyung, Kim Ho, Jin Hyung Jong
Department of Biostatistics and Epidemiology, School of Public Health, Seoul National University, 28 Yeongeon-Dong, Jongro-Gu, Seoul 110-460, Republic of Korea.
Mol Phylogenet Evol. 2009 Feb;50(2):282-9. doi: 10.1016/j.ympev.2008.10.020. Epub 2008 Nov 5.
The KsgA/Dim1 protein family of rRNA adenine dimethyltransferase (rAD) is well conserved throughout evolution. This protein family has been recognized to play multiple additional roles: as a mitochondrial transcription factor (mtTFB); as a yeast pre-rRNA cleavage enzyme (Dim1p); and as a chloroplast developmental protein (PFC1). Comprehensive phylogenetic analysis of rAD led to three main findings. First, rAD sequences were grouped by three domains of life, bacteria, archaea, and eukaryotes. Second, mtTFB shows alpha-proteobacterial endosymbiotic ancestry. Third, plastid-targeted rADs do not show cyanobacterial affiliation. Instead, plastid-targeted homologs from chlorophytes/land plants were clustered with chlamydiae, while those from rhodophytes/red algal lineage grouped with the bacteroides/chlorobi group. These unusual two-bacterial ancestries of plastid-targeted rAD suggest that bacterial genes influenced the evolution of the proteome of eukaryotic plastids in a complex way, involving more diverse bacterial groups than previously believed, and underscoring the importance of eukaryotic acquisition of bacterial functions.
rRNA腺嘌呤二甲基转移酶（rAD）的KsgA/Dim1蛋白家族在整个进化过程中高度保守。该蛋白家族还被认为具有多种其他作用：作为线粒体转录因子（mtTFB）；作为酵母前体rRNA切割酶（Dim1p）；以及作为叶绿体发育蛋白（PFC1）。对rAD的全面系统发育分析得出了三个主要发现。第一，rAD序列按生命的三个域进行分组，即细菌、古菌和真核生物。第二，mtTFB显示出α-变形菌内共生起源。第三，靶向质体的rAD不显示与蓝细菌的关联。相反，来自绿藻/陆地植物的靶向质体的同源物与衣原体聚集在一起，而来自红藻/红藻谱系的同源物则与拟杆菌/绿菌门聚集在一起。靶向质体的rAD的这些不寻常的双细菌起源表明，细菌基因以复杂的方式影响了真核质体蛋白质组的进化，涉及比以前认为的更多样化的细菌群体，并强调了真核生物获得细菌功能的重要性。
