Martin R M, Csar X F, Gasser R B, Felleisen R, Lightowlers M W
University of Melbourne, Department of Veterinary Science, Werribee, Victoria, Australia.
Parasitology. 1997 Aug;115 ( Pt 2):205-11. doi: 10.1017/s003118209700108x.
Myophilin is a muscle-associated antigen of the taeniid cestode Echinococcus granulosus. This protein shows a high amino acid sequence homology with calponins and calponin-like proteins, which are proposed to be associated with the regulation of smooth muscle contraction. In order to provide supportive evidence for a relationship between these proteins, we characterized myophilin using electrophoretic, biochemical and molecular biological approaches. Two-dimensional protein electrophoretic separation of E. granulosus larval proteins defined 4 isoelectric isoforms of myophilin (alpha, beta, gamma and delta), which appeared to be a consequence of post-translational modification of a single gene product. It was also demonstrated biochemically that E. granulosus myophilin undergoes specific phosphorylation in vitro by protein kinase C (PKC). Finally, myophilin homologues were identified in extracts of Taenia hydatigena and T. ovis by immunoblot. A partial cDNA of the closely related species, E. multilocularis, was isolated by cloning procedures and showed 99% homology with the E. granulosus myophilin gene. The similarities of E. granulosus myophilin with calponins in their tissue localization, protein isoforms patterns, ability to be phosphorylated in vitro by PKC, and the relatively conserved nature of the protein among related parasites suggest that myophilin may be associated with smooth muscle contraction.
肌纤蛋白是细粒棘球绦虫的一种与肌肉相关的抗原。该蛋白与钙调蛋白及类钙调蛋白显示出高度的氨基酸序列同源性，而这些蛋白被认为与平滑肌收缩的调节有关。为了为这些蛋白之间的关系提供支持性证据，我们采用电泳、生化及分子生物学方法对肌纤蛋白进行了表征。细粒棘球绦虫幼虫蛋白的二维电泳分离确定了肌纤蛋白的4种等电异构体（α、β、γ和δ），这似乎是单一基因产物翻译后修饰的结果。生化分析还表明，细粒棘球绦虫肌纤蛋白在体外可被蛋白激酶C（PKC）特异性磷酸化。最后，通过免疫印迹在水泡带绦虫和绵羊带绦虫的提取物中鉴定出了肌纤蛋白同源物。通过克隆程序分离出了密切相关物种多房棘球绦虫的部分cDNA，其与细粒棘球绦虫肌纤蛋白基因显示出99%的同源性。细粒棘球绦虫肌纤蛋白在组织定位、蛋白异构体模式、体外被PKC磷酸化的能力以及在相关寄生虫中该蛋白相对保守的性质方面与钙调蛋白的相似性表明，肌纤蛋白可能与平滑肌收缩有关。
