Research Program in Molecular and Integrative Biosciences, University of Helsinki, Helsinki, Finland.
Drug Research Program, Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland.
Sci Adv. 2019 May 22;5(5):eaav7574. doi: 10.1126/sciadv.aav7574. eCollection 2019 May.
Membrane-bound pyrophosphatases are homodimeric integral membrane proteins that hydrolyze pyrophosphate into orthophosphates, coupled to the active transport of protons or sodium ions across membranes. They are important in the life cycle of bacteria, archaea, plants, and parasitic protists, but no homologous proteins exist in vertebrates, making them a promising drug target. Here, we report the first nonphosphorus allosteric inhibitor of the thermophilic bacterium membrane-bound pyrophosphatase and its bound structure together with the substrate analog imidodiphosphate. The unit cell contains two protein homodimers, each binding a single inhibitor dimer near the exit channel, creating a hydrophobic clamp that inhibits the movement of β-strand 1-2 during pumping, and thus prevents the hydrophobic gate from opening. This asymmetry of inhibitor binding with respect to each homodimer provides the first clear structural demonstration of asymmetry in the catalytic cycle of membrane-bound pyrophosphatases.
膜结合焦磷酸酶是同二聚体的完整膜蛋白，可将焦磷酸盐水解为正磷酸盐，并与质子或钠离子在膜上的主动转运偶联。它们在细菌、古菌、植物和寄生原生动物的生命周期中非常重要，但脊椎动物中不存在同源蛋白，因此它们是一个很有前途的药物靶点。在这里，我们报告了第一个来自嗜热细菌膜结合焦磷酸酶的非磷变构抑制剂及其与底物类似物亚氨基二磷酸的结合结构。该单位晶胞包含两个蛋白同源二聚体，每个二聚体在出口通道附近结合一个抑制剂二聚体，形成一个疏水性夹，在泵送过程中抑制β-链 1-2 的运动，从而阻止疏水性门打开。这种抑制剂与每个同源二聚体结合的不对称性提供了膜结合焦磷酸酶催化循环中不对称性的第一个明确的结构证明。
