School of Biological Sciences and Institute for Global Food Security, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, BT9 7BL, UK.
School of Pharmacy and Biomolecular Sciences, University of Brighton, Huxley Building, Lewes Road, Brighton, BN2 4GJ, UK.
Cell Calcium. 2020 Mar;86:102161. doi: 10.1016/j.ceca.2020.102161. Epub 2020 Jan 13.
SmTAL1 is a calcium binding protein from the parasitic worm, Schistosoma mansoni. Structurally it is comprised of two domains - an N-terminal EF-hand domain and a C-terminal dynein light chain (DLC)-like domain. The protein has previously been shown to interact with the anti-schistosomal drug, praziquantel (PZQ). Here, we demonstrated that both EF-hands in the N-terminal domain are functional calcium ion binding sites. The second EF-hand appears to be more important in dictating affinity and mediating the conformational changes which occur on calcium ion binding. There is positive cooperativity between the four calcium ion binding sites in the dimeric form of SmTAL1. Both the EF-hand domain and the DLC-domain dimerise independently suggesting that both play a role in forming the SmTAL1 dimer. SmTAL1 binds non-cooperatively to PZQ and cooperatively to an IQ-motif from SmCa1B, a voltage-gated calcium channel. PZQ tends to strengthen this interaction, although the relationship is complex. These data suggest the hypothesis that SmTAL1 regulates at least one voltage-gated calcium channel and PZQ interferes with this process. This may be important in the molecular mechanism of this drug. It also suggests that compounds which bind SmTAL1, such as six from the Medicines for Malaria Box identified in this work, may represent possible leads for the discovery of novel antagonists.
SmTAL1 是一种来自寄生蠕虫曼氏血吸虫的钙结合蛋白。从结构上看，它由两个结构域组成——一个 N 端 EF 手结构域和一个 C 端肌球蛋白轻链（DLC）样结构域。该蛋白先前已被证明与抗血吸虫药物吡喹酮（PZQ）相互作用。在这里，我们证明了 N 端结构域中的两个 EF 手都是功能性钙离子结合位点。第二个 EF 手似乎在决定亲和力和介导钙离子结合时发生的构象变化方面更为重要。SmTAL1 二聚体的四个钙离子结合位点之间存在正协同作用。EF 手结构域和 DLC 结构域都可以独立地二聚化，这表明它们都在形成 SmTAL1 二聚体中发挥作用。SmTAL1 与 PZQ 非协同结合，并与电压门控钙通道 SmCa1B 的 IQ 基序协同结合。PZQ 往往会增强这种相互作用，尽管这种关系很复杂。这些数据表明了这样一种假设，即 SmTAL1 至少调节一种电压门控钙通道，而 PZQ 干扰这一过程。这在这种药物的分子机制中可能很重要。这也表明，与 SmTAL1 结合的化合物，如本文中从抗疟疾药物盒中确定的六种化合物，可能代表发现新型拮抗剂的潜在先导化合物。
