de Walque S, Kiel J A, Veenhuis M, Opperdoes F R, Michels P A
Research Unit for Tropical Diseases, Christian de Duve Institute of Cellular Pathology and Laboratory of Biochemistry, Université Catholique de Louvain, Brussels, Belgium.
Mol Biochem Parasitol. 1999 Oct 25;104(1):106-19. doi: 10.1016/s0166-6851(99)00144-9.
Kinetoplastid organisms, such as the protozoan parasite Trypanosoma brucei, compartmentalise several important metabolic pathways in organelles called glycosomes. Glycosomes are related to peroxisomes of yeast and mammalian cells. A subset of glycosomal matrix proteins is routed to the organelles via the peroxisome-targeting signal type 1 (PTS-1). The PEX5 gene homologue has been cloned from T. brucei coding for a protein of the translocation machinery, the PTS-1 receptor. The gene codes for a polypeptide of 654 amino acids with a calculated molecular mass of 70 kDa. Like its homologue in other organisms T. brucei PTS-1 receptor protein (TbPEX5) is a member of the tetratricopeptide repeat (TPR) protein family and contains several copies of the pentapeptide W-X-X-X-F/Y. Northern and Western blot analysis showed that the protein is expressed at different stages of the life cycle of the parasite. The protein has been overproduced in Escherichia coli and purified using immobilized metal affinity chromatography. The purified protein specifically interacts in vitro with glycosomal phosphoglycerate kinase-C (PGK-C) of T. brucei, a PTS-1 containing protein. The equilibrium dissociation constant (Kd) of PGK-C for purified TbPEX5 is 40 nM. Using biochemical and cytochemical techniques a predominantly cytosolic localization was found for TbPEX5. This is consistent with the idea of receptor cycling between the glycosomes and the cytosol.
动质体生物，如原生动物寄生虫布氏锥虫，将几种重要的代谢途径分隔在称为糖体的细胞器中。糖体与酵母和哺乳动物细胞的过氧化物酶体相关。一部分糖体基质蛋白通过1型过氧化物酶体靶向信号（PTS-1）被输送到细胞器。已从布氏锥虫中克隆出PEX5基因同源物，其编码转运机制中的一种蛋白质，即PTS-1受体。该基因编码一个由654个氨基酸组成的多肽，计算分子量为70 kDa。与其他生物中的同源物一样，布氏锥虫PTS-1受体蛋白（TbPEX5）是四肽重复（TPR）蛋白家族的成员，包含多个五肽W-X-X-X-F/Y拷贝。Northern和Western印迹分析表明，该蛋白在寄生虫生命周期的不同阶段表达。该蛋白已在大肠杆菌中过量表达，并使用固定化金属亲和色谱法进行纯化。纯化后的蛋白在体外与布氏锥虫的糖体磷酸甘油酸激酶-C（PGK-C，一种含PTS-1的蛋白）特异性相互作用。PGK-C与纯化后的TbPEX5的平衡解离常数（Kd）为40 nM。使用生化和细胞化学技术发现TbPEX5主要定位于细胞质。这与受体在糖体和细胞质之间循环的观点一致。
