Jacobs D, Dubremetz J F, Loyens A, Bosman F, Saman E
Innogenetics N.V., Gent, Belgium.
Mol Biochem Parasitol. 1998 Mar 15;91(2):237-49. doi: 10.1016/s0166-6851(97)00204-1.
Immunoscreening of an expression library constructed with Toxoplasma gondii tachyzoite mRNA with sera from toxoplasmosis-positive humans has led to the identification of a new parasite antigen. Sequence analysis of the gene encoding this antigen allowed the calculation of the theoretical molecular mass (25,857 Da) and showed that the protein contains a putative signal sequence. The C-terminal region contains two hydrophobic regions, the last of which has the characteristics of a membrane-spanning domain. When the protein was heterologously expressed in E. coli and tested by Western blot, it reacted with the human sera originally used for screening. The new antigen also reacted with a monoclonal antibody raised against the entire parasite. Ultrastructural analysis showed that the protein is localized in the dense granules. After host cell invasion, the protein is secreted into the vacuolar network, the parasitophorous vacuole membrane, and into extensions protruding in the cytoplasm. Therefore, it is suggested to designate this new dense granule protein GRA7, following the established nomenclature for this protein family.
用弓形虫速殖子mRNA构建表达文库，并用弓形虫病阳性患者的血清进行免疫筛选，从而鉴定出一种新的寄生虫抗原。对编码该抗原的基因进行序列分析，计算出其理论分子量为25,857道尔顿，并表明该蛋白含有一个推定的信号序列。C末端区域包含两个疏水区域，其中最后一个具有跨膜结构域的特征。当该蛋白在大肠杆菌中进行异源表达并通过蛋白质印迹法检测时，它与最初用于筛选的人血清发生反应。这种新抗原还与针对整个寄生虫产生的单克隆抗体发生反应。超微结构分析表明，该蛋白定位于致密颗粒中。宿主细胞被侵袭后，该蛋白被分泌到液泡网络、寄生泡膜以及向细胞质中突出的延伸部分。因此，按照该蛋白家族已确立的命名法，建议将这种新的致密颗粒蛋白命名为GRA7。
