Dunn P P, Bumstead J M, Tomley F M
Institute for Animal Health, Compton, Newbury, Berkshire, UK.
Parasitology. 1996 Nov;113 ( Pt 5):439-48. doi: 10.1017/s0031182000081506.
We have isolated and sequenced cDNA clones from Eimeria tenella and Eimeria maxima which encode proteins that share homology with a recently described family of calmodulin-domain protein kinases. The primary sequence data show that each of the protein kinases can be divided into 2 main functional domains-an amino-terminal catalytic domain typical of serine/threonine protein kinases and a carboxy-terminal domain homologous to calmodulin, which is capable of binding calcium ions at 4 'EF-hand' motifs. Expression of the E. tenella calmodulin-domain protein kinase (EtCDPK) increased towards the end of oocyst sporulation, as judged by Northern and Western blotting, and indirect immunofluorescent antibody labelling showed that within a few minutes of adding sporozoites to target host cells in in vitro culture EtCDPK was found to be specifically associated with a filament-like structure that converges at the apical end of the parasite. Once the parasite entered the host cell EtCDPK appeared to be left on the host cell membrane at the point of entry, indicating a brief yet specific role for this molecule in the invasion of host cells by E. tenella.
我们已经从柔嫩艾美耳球虫和巨型艾美耳球虫中分离并测序了cDNA克隆，这些克隆编码的蛋白质与最近描述的钙调蛋白结构域蛋白激酶家族具有同源性。一级序列数据表明，每种蛋白激酶都可分为2个主要功能域——一个氨基末端催化结构域，这是丝氨酸/苏氨酸蛋白激酶的典型结构域，以及一个与钙调蛋白同源的羧基末端结构域，该结构域能够在4个“EF-手型”基序处结合钙离子。通过Northern印迹和Western印迹判断，柔嫩艾美耳球虫钙调蛋白结构域蛋白激酶（EtCDPK）的表达在卵囊孢子化末期增加，间接免疫荧光抗体标记显示，在体外培养中将子孢子添加到靶宿主细胞后的几分钟内，发现EtCDPK与一种丝状结构特异性相关，该结构在寄生虫顶端汇聚。一旦寄生虫进入宿主细胞，EtCDPK似乎就留在宿主细胞膜的进入点处，表明该分子在柔嫩艾美耳球虫入侵宿主细胞过程中具有短暂而特定的作用。
