Abid Hela, Harigua-Souiai Emna, Mejri Thouraya, Barhoumi Mourad, Guizani Ikram
Laboratory of Molecular Epidemiology and Experimental Pathology (LR11IPT04/ LR16IPT04), Institut Pasteur de Tunis, Université de Tunis El Manar, Tunis, Tunisia.
Faculté des Sciences de Bizerte, Université de Carthage, Tunis, Tunisie.
BMC Struct Biol. 2017 Dec 19;17(1):9. doi: 10.1186/s12900-017-0079-7.
The 5'-methylthioadenosine phosphorylase (MTAP), an enzyme involved in purine and polyamine metabolism and in the methionine salvage pathway, is considered as a potential drug target against cancer and trypanosomiasis. In fact, Trypanosoma and Leishmania parasites lack de novo purine pathways and rely on purine salvage pathways to meet their requirements. Herein, we propose the first comprehensive bioinformatic and structural characterization of the putative Leishmania infantum MTAP (LiMTAP), using a comparative computational approach.
Sequence analysis showed that LiMTAP shared higher identity rates with the Trypanosoma brucei (TbMTAP) and the human (huMTAP) homologs as compared to the human purine nucleoside phosphorylase (huPNP). Motifs search using MEME identified more common patterns and higher relatedness of the parasite proteins to the huMTAP than to the huPNP. The 3D structures of LiMTAP and TbMTAP were predicted by homology modeling and compared to the crystal structure of the huMTAP. These models presented conserved secondary structures compared to the huMTAP, with a similar topology corresponding to the Rossmann fold. This confirmed that both LiMTAP and TbMTAP are members of the NP-I family. In comparison to the huMTAP, the 3D model of LiMTAP showed an additional α-helix, at the C terminal extremity. One peptide located in this specific region was used to generate a specific antibody to LiMTAP. In comparison with the active site (AS) of huMTAP, the parasite ASs presented significant differences in the shape and the electrostatic potentials (EPs). Molecular docking of 5'-methylthioadenosine (MTA) and 5'-hydroxyethylthio-adenosine (HETA) on the ASs on the three proteins predicted differential binding modes and interactions when comparing the parasite proteins to the human orthologue.
This study highlighted significant structural peculiarities, corresponding to functionally relevant sequence divergence in LiMTAP, making of it a potential drug target against Leishmania.
5'-甲硫腺苷磷酸化酶（MTAP）是一种参与嘌呤和多胺代谢以及甲硫氨酸补救途径的酶，被认为是对抗癌症和锥虫病的潜在药物靶点。事实上，锥虫和利什曼原虫寄生虫缺乏从头合成嘌呤途径，依赖嘌呤补救途径来满足其需求。在此，我们使用比较计算方法，首次对推测的婴儿利什曼原虫MTAP（LiMTAP）进行了全面的生物信息学和结构表征。
序列分析表明，与人类嘌呤核苷磷酸化酶（huPNP）相比，LiMTAP与布氏锥虫（TbMTAP）和人类（huMTAP）同源物的同源率更高。使用MEME进行的基序搜索发现，寄生虫蛋白与huMTAP的共同模式更多，相关性更高，而与huPNP的相关性较低。通过同源建模预测了LiMTAP和TbMTAP的三维结构，并与huMTAP的晶体结构进行了比较。与huMTAP相比，这些模型呈现出保守的二级结构，具有与罗斯曼折叠相对应的相似拓扑结构。这证实了LiMTAP和TbMTAP都是NP-I家族的成员。与huMTAP相比，LiMTAP的三维模型在C末端有一个额外的α螺旋。位于该特定区域的一个肽段被用于生成针对LiMTAP的特异性抗体。与huMTAP的活性位点（AS）相比，寄生虫的AS在形状和静电势（EP）方面存在显著差异。当将寄生虫蛋白与人类直系同源物进行比较时，5'-甲硫腺苷（MTA）和5'-羟乙基硫代腺苷（HETA）在这三种蛋白的AS上的分子对接预测了不同的结合模式和相互作用。
本研究突出了LiMTAP中与功能相关的序列差异相对应的显著结构特点，使其成为对抗利什曼原虫的潜在药物靶点。
