Bromley Elizabeth V, Taylor Martin C, Wilkinson Shane R, Kelly John M
Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.
Int J Parasitol. 2004 Jan;34(1):63-71. doi: 10.1016/j.ijpara.2003.09.004.
WD (tryptophan/aspartic acid) repeat proteins perform a wide variety of functions in eukaryotic cells. They are characterised by the presence of a number of conserved repeat motifs that contribute to the beta-propeller structures which are the common feature of this large group of proteins. We report here the properties of the first characterised member of this family in the American trypanosome, Trypanosoma cruzi (TcBPP1). In the CL Brener clone the protein is 482 amino acids long and is predicted to contain four WD repeat motifs, flanked by amino and carboxyl terminal extensions. TcBPP1 is a single copy gene present on a 1.0/1.6 Mb pair of homologous chromosomes in a locus that is syntenic with the corresponding regions of Trypanosoma brucei and Leishmania major chromosomes. Consistent with the proposed hybrid nature of the CL Brener clone, the proteins encoded by the two different alleles share only 97% identity at the amino acid level. To determine subcellular location, we examined transfected parasites for the distribution of green fluorescent protein (GFP) fused with different regions of TcBPP1. These studies demonstrated that a 115 amino acid peptide derived from the amino terminal domain of TcBPP1 is able to target GFP to the mitochondrion. Interestingly this region lacks a typical amino terminal presequence suggesting that mitochondrial import is mediated by an alternative targeting signal.
WD（色氨酸/天冬氨酸）重复蛋白在真核细胞中执行多种功能。它们的特征是存在许多保守的重复基序，这些基序有助于形成β-螺旋桨结构，这是这一大类蛋白质的共同特征。我们在此报告美洲锥虫克氏锥虫（TcBPP1）中该家族首个被表征成员的特性。在CL Brener克隆中，该蛋白长度为482个氨基酸，预计包含四个WD重复基序，两侧为氨基末端和羧基末端延伸。TcBPP1是一个单拷贝基因，存在于一对1.0/1.6 Mb的同源染色体上，其所在位点与布氏锥虫和硕大利什曼原虫染色体相应区域是同线的。与CL Brener克隆的推测杂种性质一致，由两个不同等位基因编码的蛋白质在氨基酸水平上仅具有97%的同一性。为了确定亚细胞定位，我们检测了转染的寄生虫中与TcBPP1不同区域融合的绿色荧光蛋白（GFP）的分布。这些研究表明，源自TcBPP1氨基末端结构域的115个氨基酸的肽能够将GFP靶向到线粒体。有趣的是，该区域缺乏典型的氨基末端前序列，这表明线粒体导入是由一种替代靶向信号介导的。
