Mingler Melissa K, Hingst Andrea M, Clement Sandra L, Yu Laura E, Reifur Larissa, Koslowsky Donna J
Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA.
Mol Biochem Parasitol. 2006 Nov;150(1):37-45. doi: 10.1016/j.molbiopara.2006.06.006. Epub 2006 Jun 28.
A new class of organellar proteins, characterized by pentatricopeptide repeat (PPR) motifs, has been identified in plants. These proteins contain multiple 35-amino acid repeats that are proposed to form a super helix capable of binding a strand of RNA. All PPR proteins characterized to date appear to be involved in RNA processing pathways in organelles. Twenty-three PPR proteins have been identified in Trypanosoma brucei and database research indicates that most of these proteins are predicted to contain the traditional mitochondrial target sequence. Orthologues of each of the 23 proteins have also been identified in Leishmania major and Trypanosoma cruzi, indicating that these proteins represent a highly conserved class of proteins within the kinetoplastid family. Preliminary experiments using RNAi to specifically silence one identified PPR gene (TbPPRl- Tb927.2.3180), indicate that cells depleted of TbPPRl transcripts show a slow growth phenotype and altered mitochondrial maxicircle RNA profiles. This initial characterization suggests that PPR proteins will play important roles in the complex RNA processing required for mitochondrial gene expression in trypanosomes.
在植物中已鉴定出一类新的细胞器蛋白，其特征为含有五肽重复序列（PPR）基序。这些蛋白质包含多个35个氨基酸的重复序列，据推测这些重复序列可形成一个能够结合RNA链的超螺旋结构。迄今为止所鉴定的所有PPR蛋白似乎都参与细胞器中的RNA加工途径。在布氏锥虫中已鉴定出23种PPR蛋白，数据库研究表明，这些蛋白中的大多数预计含有传统的线粒体靶向序列。在硕大利什曼原虫和克氏锥虫中也鉴定出了这23种蛋白中的每一种的直系同源物，这表明这些蛋白代表了动基体目家族中一类高度保守的蛋白。使用RNA干扰特异性沉默一个已鉴定的PPR基因（TbPPR1 - Tb927.2.3180）的初步实验表明，缺乏TbPPR1转录本的细胞表现出生长缓慢的表型以及线粒体大环RNA图谱的改变。这一初步特征表明，PPR蛋白将在锥虫线粒体基因表达所需的复杂RNA加工过程中发挥重要作用。
