Donahue C G, Carruthers V B, Gilk S D, Ward G E
Department of Microbiology and Molecular Genetics, University of Vermont, 214 Stafford Hall, Burlington, VT 05405, USA.
Mol Biochem Parasitol. 2000 Nov;111(1):15-30. doi: 10.1016/s0166-6851(00)00289-9.
A monoclonal antibody (MAb) has been generated against a novel 63 kDa surface/apical antigen of Toxoplasma gondii tachyzoites which is identified here as TgAMA-1, the Toxoplasma homolog of Plasmodium apical membrane antigen-1 (AMA-1). Sequence analysis, phase partitioning in Triton X-114, and labeling of TgAMA-1 with iodonaphthalene azide all suggest that TgAMA-1 is a type I transmembrane protein. There is a high degree of sequence similarity between TgAMA-1 and Plasmodium AMA-1, most notably in the position of conserved cysteine residues within the protein's predicted extracellular domain. In contrast to full length Plasmodium AMA-1, which has previously been localized to the rhoptries, it is shown here by immunofluorescence and immunoelectron microscopy that intracellular TgAMA-1 is found in the micronemes. A 53 kDa N-terminal proteolytic fragment of TgAMA-1 is constitutively secreted from the parasite at 37 degrees C. As is the case with other microneme proteins, the proteolytic processing and secretion of TgAMA-1 is dramatically enhanced in response to treatments which increase intracellular calcium levels.
已产生一种针对刚地弓形虫速殖子新型63 kDa表面/顶端抗原的单克隆抗体（MAb），在此将其鉴定为TgAMA-1，即疟原虫顶端膜抗原-1（AMA-1）的弓形虫同源物。序列分析、在Triton X-114中的相分配以及用碘萘叠氮化物标记TgAMA-1均表明TgAMA-1是一种I型跨膜蛋白。TgAMA-1与疟原虫AMA-1之间存在高度的序列相似性，最显著的是在该蛋白预测的细胞外结构域内保守半胱氨酸残基的位置。与先前定位于棒状体的全长疟原虫AMA-1不同，免疫荧光和免疫电子显微镜在此显示细胞内的TgAMA-1存在于微线体中。TgAMA-1的一个53 kDa N端蛋白水解片段在37℃时从寄生虫中组成性分泌。与其他微线体蛋白一样，TgAMA-1的蛋白水解加工和分泌在响应增加细胞内钙水平的处理时会显著增强。
