Biological Sciences, Indian Institute of Science Education and Research, Kolkata, India.
Curr Microbiol. 2011 Apr;62(4):1179-84. doi: 10.1007/s00284-010-9845-5. Epub 2010 Dec 17.
The morphology of the endomembrane system of Giardia lamblia appears to be significantly different from higher eukaryotes. Therefore, the molecular mechanisms controlling vesicular trafficking are also likely to be altered. Since FYVE domain is a known regulator of endosomal trafficking, the authors used BLAST search to identify FYVE domain(s) in G. lamblia. A 990 amino acid long putative FYVE domain-containing ORF was identified, which contains all the conserved sequence elements in the ligand binding pocket. Phylogenetic analysis reveals that this domain is significantly diverged. The authors have shown that the corresponding gene is expressed in G. lamblia trophozoites and cysts. In spite of this phylogenetic divergence, in vitro biochemical assay indicates that this domain preferentially binds to phosphatidylinositol 3-phosphate {PtdIns(3)P}and in vivo expression of the GFP-tagged G. lamblia FYVE domain in S. cerevisiae, displays its selective localization to PtdIns(3)P-enriched endosomes. This is the first study to characterize a PtdIns(3)P effector protein in this early-diverged eukaryote.
贾第虫的内膜系统形态似乎与高等真核生物明显不同。因此，控制囊泡运输的分子机制也可能发生改变。由于 FYVE 结构域是已知的内体运输调节剂，作者使用 BLAST 搜索来鉴定 G. lamblia 中的 FYVE 结构域。鉴定到一个 990 个氨基酸长的假定 FYVE 结构域包含体，其中包含配体结合口袋中的所有保守序列元件。系统发育分析表明，该结构域存在显著差异。作者已经表明，相应的基因在 G. lamblia 滋养体和包囊中有表达。尽管存在这种系统发育分歧，但体外生化测定表明，该结构域优先结合磷脂酰肌醇 3-磷酸（PtdIns(3)P），并且在 S. cerevisiae 中表达 GFP 标记的 G. lamblia FYVE 结构域，显示其选择性定位于富含 PtdIns(3)P 的内体。这是首次在这种早期分化的真核生物中表征 PtdIns(3)P 效应蛋白的研究。
