Inositol Signaling Group, Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, USA.
Nat Chem Biol. 2011 Nov 27;8(1):111-6. doi: 10.1038/nchembio.733.
Inositol pyrophosphates (such as IP7 and IP8) are multifunctional signaling molecules that regulate diverse cellular activities. Inositol pyrophosphates have 'high-energy' phosphoanhydride bonds, so their enzymatic synthesis requires that a substantial energy barrier to the transition state be overcome. Additionally, inositol pyrophosphate kinases can show stringent ligand specificity, despite the need to accommodate the steric bulk and intense electronegativity of nature's most concentrated three-dimensional array of phosphate groups. Here we examine how these catalytic challenges are met by describing the structure and reaction cycle of an inositol pyrophosphate kinase at the atomic level. We obtained crystal structures of the kinase domain of human PPIP5K2 complexed with nucleotide cofactors and either substrates, product or a MgF(3)(-) transition-state mimic. We describe the enzyme's conformational dynamics, its unprecedented topological presentation of nucleotide and inositol phosphate, and the charge balance that facilitates partly associative in-line phosphoryl transfer.
肌醇六磷酸（如 IP7 和 IP8）是多功能信号分子，可调节多种细胞活动。肌醇六磷酸具有“高能”磷酸酐键，因此其酶促合成需要克服过渡态的大量能量障碍。此外，尽管需要适应自然界最集中的三维磷酸盐基团的巨大体积和强烈的电负性，但肌醇六磷酸激酶可以表现出严格的配体特异性。在这里，我们通过描述肌醇六磷酸激酶在原子水平上的结构和反应循环来研究如何应对这些催化挑战。我们获得了与人 PPIP5K2 激酶结构域与核苷酸辅因子和底物、产物或 MgF(3)(-)过渡态模拟物复合物的晶体结构。我们描述了酶的构象动力学、其核苷酸和肌醇磷酸的前所未有的拓扑结构，以及促进部分缔合在线磷酰基转移的电荷平衡。
