Heintzelman Matthew B
Department of Anatomy, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Cell Motil Cytoskeleton. 2004 Jun;58(2):83-95. doi: 10.1002/cm.10178.
Actin and two class XIV unconventional myosins have been cloned from Gregarina polymorpha, a large protozoan parasite inhabiting the gut of the mealworm Tenebrio molitor. These proteins were most similar to their homologues expressed in the coccidian and haemosporidian Apicomplexa such as Toxoplasma and Plasmodium despite the significant morphological differences among these parasites. Both actin and G. polymorpha myosin A (GpMyoA), a 92.6-kDa protein characterized by a canonical myosin head domain and short, highly basic tail, localized to both the longitudinally-disposed surface membrane folds (epicytic folds) of the parasite as well as to the subjacent rib-like myonemes that gird the parasite cortex. G. polymorpha myosin B (GpMyoB), a 96.3-kDa myosin, localized exclusively to the epicytic folds of the parasite. Both myosins were tightly associated with the cortical cytoskeleton and were solubilized only with a combination of high salt and detergent. Both GpMyoA and GpMyoB could bind to actin in an ATP-sensitive fashion. The distribution of actin and the unconventional myosins in G. polymorpha was consistent with their proposed participation in both the rapid (1-10 microm/sec) gliding motility exhibited by the gregarines as well as the myoneme-mediated bending motions that have been observed in these parasites.
肌动蛋白和两种十四类非传统肌球蛋白已从多形簇虫（Gregarina polymorpha）中克隆出来，多形簇虫是一种寄生于黄粉虫（Tenebrio molitor）肠道的大型原生动物寄生虫。尽管这些寄生虫在形态上存在显著差异，但这些蛋白质与在球虫和血孢子虫等顶复门生物（如弓形虫和疟原虫）中表达的同源物最为相似。肌动蛋白和多形簇虫肌球蛋白A（GpMyoA，一种92.6 kDa的蛋白质，其特征为具有典型的肌球蛋白头部结构域和短的、高度碱性的尾部）均定位于寄生虫纵向排列的表面膜褶皱（表膜褶皱）以及环绕寄生虫皮层的下方肋状肌原纤维。多形簇虫肌球蛋白B（GpMyoB，一种96.3 kDa的肌球蛋白）仅定位于寄生虫的表膜褶皱。两种肌球蛋白均与皮层细胞骨架紧密相连，并且仅在高盐和去污剂的组合作用下才会溶解。GpMyoA和GpMyoB都能以ATP敏感的方式与肌动蛋白结合。肌动蛋白和非传统肌球蛋白在多形簇虫中的分布与其参与簇虫所表现出的快速（1 - 10微米/秒）滑行运动以及在这些寄生虫中观察到的肌原纤维介导的弯曲运动的推测一致。
