Quevillon Emmanuel, Spielmann Tobias, Brahimi Karima, Chattopadhyay Debasish, Yeramian Edouard, Langsley Gordon
Laboratoire de Signalisation Immunoparasitaire, URA CNRS 1960, Department of Parasitology, Institut Pasteur, Paris, France.
Gene. 2003 Mar 13;306:13-25. doi: 10.1016/s0378-1119(03)00381-0.
Rab GTPases are key regulators of vesicular traffic in eukaryotic cells. Here we sought a global characterization and description of the Plasmodium falciparum family of Rab GTPases. We used a combination of bioinformatic analyses, experimental testing of predictions, structure modelling and phylogenetics. These analyses led to the identification of seven new parasite Rabs. Accordingly we estimate that the P. falciparum family is made up of 11 genes. We show that ten members of this family are transcribed in infected erythrocytes. Concerning the various members of the family, a series of specific as well as global conclusions can be drawn. Rabs predicted to be compartment-specific show different subcellular distributions. This is demonstrated for PfRab1A and PfRab11A, with the generation of specific antisera. The sequence analyses reveal several peculiarities, with possible functional implications. One of the transcribed genes, Pfrab5b, does not encode a classical C-terminus, suggestive of a novel regulatory role for this GTPase. Another, Pfrab5a, previously identified as a rab gene located on chromosome 2, possesses a 30-amino-acid insertion in its GTP-binding domain. Structural considerations suggest that this insertion could represent a novel interaction interface. We used conserved RabF and RabSF motifs to discriminate between specific parasite Rabs, and followed their predicted change in position on the structure of PfRab6, as GTP is hydrolysed to GDP. This allowed us to propose their involvement in potential interaction surfaces, that we extended to human Rab6 and the motifs known to mediate Rabkinesine-6 binding. Finally, we compared the P. falciparum Rab family to those of Saccharomyces cerevisiae and Schizosaccharomyces pombe and found that parasite Rabs segregate into possible functional clads. Such grouping into clads may give clues to parasite Rab function, and may shed light on P. falciparum secretory/endocytic pathways.
Rab GTP酶是真核细胞中囊泡运输的关键调节因子。在此，我们旨在对恶性疟原虫Rab GTP酶家族进行全面的特征描述。我们结合了生物信息学分析、预测的实验验证、结构建模和系统发育分析。这些分析鉴定出了7个新的寄生虫Rab。据此，我们估计恶性疟原虫家族由11个基因组成。我们发现该家族的10个成员在受感染的红细胞中被转录。关于该家族的各个成员，可以得出一系列具体以及总体的结论。预测为特定区室特异性的Rab显示出不同的亚细胞分布。通过生成特异性抗血清，PfRab1A和PfRab11A的情况得以证明。序列分析揭示了几个特点，可能具有功能上的意义。其中一个转录基因Pfrab5b不编码经典的C末端，提示该GTP酶具有新的调节作用。另一个基因Pfrab5a，先前被鉴定为位于2号染色体上的rab基因，在其GTP结合结构域中有一个30个氨基酸的插入。结构方面的考虑表明，这个插入可能代表一个新的相互作用界面。我们使用保守的RabF和RabSF基序来区分特定的寄生虫Rab，并追踪它们在PfRab6结构上随着GTP水解为GDP而预测的位置变化。这使我们能够提出它们参与潜在的相互作用表面，我们将其扩展到人类Rab6以及已知介导Rabkinesine - 6结合的基序。最后，我们将恶性疟原虫Rab家族与酿酒酵母和粟酒裂殖酵母的Rab家族进行了比较，发现寄生虫Rab可分为可能的功能类群。这种分类为功能类群可能为寄生虫Rab的功能提供线索，并可能揭示恶性疟原虫的分泌/内吞途径。
