El Hajj Hiba, Demey Emmanuelle, Poncet Joël, Lebrun Maryse, Wu Bo, Galéotti Nathalie, Fourmaux Marie Noëlle, Mercereau-Puijalon Odile, Vial Henri, Labesse Gilles, Dubremetz Jean François
UMR 5539 CNRS, Université de Montpellier 2, Place E. Bataillon, Montpellier, France.
Proteomics. 2006 Nov;6(21):5773-84. doi: 10.1002/pmic.200600187.
Four rhoptry proteins (ROP) of Toxoplasma gondii previously identified with mAb have been affinity purified and analyzed by MS; the data obtained allowed the genomic sequences to be assigned to these proteins. As previously suggested for some of them by antibody crossreactivity, these proteins were shown to belong to a family, the prototype of which being ROP2. We describe here the proteins ROP2, 4, 5, and 7. These four proteins correspond to the most abundant products of a gene family that comprises several members which we have identified in genomic and EST libraries. Eight additional sequences were found and we have cloned four of them. All members of the ROP2 family contain a protein-kinase-like domain, but only some of them possess a bona fide kinase catalytic site. Molecular modeling of the kinase domain demonstrates the conservation of residues critical for the stabilization of the protein-kinase fold, especially within a hydrophobic segment described so far as transmembrane and which appears as an helix buried inside the protein. The concomitant synthesis of these ROPs by T. gondii tachyzoites suggests a specific role for each of these proteins, especially in the early interaction with the host cell upon invasion.
先前用单克隆抗体鉴定出的刚地弓形虫的四种棒状体蛋白（ROP）已通过亲和纯化并进行质谱分析；所获得的数据使这些蛋白的基因组序列得以确定。正如先前通过抗体交叉反应对其中一些蛋白所推测的那样，这些蛋白被证明属于一个家族，其原型为ROP2。我们在此描述ROP2、4、5和7这几种蛋白。这四种蛋白对应于一个基因家族中最丰富的产物，该家族包含我们在基因组文库和EST文库中鉴定出的多个成员。还发现了另外八个序列，我们已克隆了其中四个。ROP2家族的所有成员都含有一个类蛋白激酶结构域，但只有其中一些具有真正的激酶催化位点。激酶结构域的分子建模表明，对于稳定蛋白激酶折叠至关重要的残基是保守的，尤其是在一个迄今为止被描述为跨膜的疏水片段内，该片段呈现为埋在蛋白内部的螺旋结构。刚地弓形虫速殖子同时合成这些ROP表明这些蛋白各自具有特定作用，尤其是在入侵时与宿主细胞的早期相互作用中。
