Molecular characterization of TgMIC5, a proteolytically processed antigen secreted from the micronemes of Toxoplasma gondii
Molecular characterization of TgMIC5, a proteolytically processed antigen secreted from the micronemes of Toxoplasma gondii
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DOI：
10.1016/s0166-6851(00)00296-6
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发表时间：
2000-11-01
影响因子：
1.5
通讯作者：
Carruthers, VB
中科院分区：
文献类型：
--
作者：
Brydges, SD;Sherman, GD;Carruthers, VB
在侵入宿主细胞的过程中，弓形虫释放位于顶端的小分泌细胞器（称为微丝）的内容物。已知寄生丝蛋白是寄生虫运动和侵入宿主细胞所必需的。为了进一步确定弓形虫微线的内容，我们使用细胞分级分离和分泌调节药物，以确定六个新的，推定的微线蛋白。在本文中，我们描述了这些新的蛋白质之一，TgMIC 5的初步表征。TgMIC 5 cDNA和基因的分子克隆和DNA序列分析显示，它编码一种以前鉴定的免疫显性抗原，称为H4。TgMIC 5还具有肽基-脯氨酰顺反异构酶（PPI酶）的小蛋白家族成员特有的共有序列。TgMIC 5表达为前原蛋白，其在进一步加工成22 kDa的成熟蛋白之前通过信号肽酶蛋白水解加工成前蛋白。结合蛋白分泌实验、免疫荧光和免疫电镜，我们证明了TgMIC 2储存在T.弓形虫速殖子在分泌到周围介质中之前。基于其与小蛋白样PPIases的同源性，TgMIC 5可能有助于其他微线蛋白的折叠，这些微线蛋白在T.弓形虫速殖子(C)2000 Elsevier Science B. V.保留所有权利。
During invasion of host cells, Toxoplasma gondii discharges the contents of small, apically located secretory organelles called micronemes. Micronemal proteins are known to be necessary for both parasite motility and invasion of host cells. To further define the contents of Toxoplasma micronemes, we used cell fractionation and secretion-modulating drugs to identify six novel, putative micronemal proteins. In this paper we describe preliminary characterization of one of these novel proteins, TgMIC5. Molecular cloning and DNA sequence analysis of the TgMIC5 cDNA and gene revealed that it encodes a previously identified immunodominant antigen called H4. TgMIC5 also possesses a consensus sequence unique to members of the parvulin family of peptidyl-prolyl cis-trans isomerases (PPIases). TgMIC5 is expressed as a preproprotein, which is proteolytically processed to a proprotein by signal peptidase before being further processed to a mature protein of 22 kDa. Using a combination of protein secretion experiments, immunofluorescence and immunoelectron microscopy, we demonstrated that TgMIC2 is stored in the micronemes of T. gondii tachyzoites before it is secreted into the surrounding medium. Based on its homology with parvulin-like PPIases, TgMIC5 may assist in the folding of other micronemal proteins that function in invasion of host cells by T. gondii tachyzoites. (C) 2000 Elsevier Science B.V. All rights reserved.