Klein H, Mehlhorn H, Rüger W
Fakultät für Biologie, Arbeitsgruppe Molekulare Genetik, Ruhr-Universität Bochum, Germany.
Parasitol Res. 1996;82(5):468-74. doi: 10.1007/s004360050146.
The cDNA clone pSM/1.6 encoding the 26.5-kDa precursor molecule of the 16/17-kDa microneme antigen of Sarcocystis muris cyst merozoites was expressed in a cell-free translation/translocation system to study translocation of the protein across membranes. The antigen was found to be translocated across heterologous endoplasmic reticulum membranes. Translocation was accompanied by cleavage of a signal peptide to create a 23-kDa polypeptide that was completely protected from digestion with proteinase K. Pulse-chase analysis of [35S]-methionine-labeled S. muris cyst merozoites demonstrated that the 16/17-kDa antigen derived from a 23-kDa precursor molecule and that its processing occurred at between a few minutes and 2 h after biosynthesis. This leads to the conclusion that the native microneme antigen is secreted from the parasite cell via the endoplasmic reticulum. Sorting into micronemes might occur during transition through a Golgi-like structure, involving cleavage of the hydrophilic propeptide to create the mature 16/17-kDa protein.
编码鼠肉孢子虫包囊裂殖子16/17-kDa微线体抗原26.5-kDa前体分子的cDNA克隆pSM/1.6在无细胞翻译/转运系统中表达，以研究该蛋白跨膜转运情况。发现该抗原可跨异源内质网膜转运。转运过程伴随着信号肽的切割，产生一个23-kDa的多肽，该多肽完全不受蛋白酶K消化的影响。对[35S]-甲硫氨酸标记的鼠肉孢子虫包囊裂殖子进行脉冲追踪分析表明，16/17-kDa抗原来源于一个23-kDa的前体分子，其加工过程发生在生物合成后的几分钟到2小时之间。由此得出结论，天然微线体抗原通过内质网从寄生虫细胞中分泌出来。在通过类似高尔基体的结构过渡期间可能会发生微线体分选，这涉及亲水性前肽的切割以产生成熟的16/17-kDa蛋白。
