Noble M E, Wierenga R K, Lambeir A M, Opperdoes F R, Thunnissen A M, Kalk K H, Groendijk H, Hol W G
European Molecular Biology Laboratory, Heidelberg, Federal Republic of Germany.
Proteins. 1991;10(1):50-69. doi: 10.1002/prot.340100106.
Crystals of triosephosphate isomerase from Trypanosoma brucei brucei have been used in binding studies with three competitive inhibitors of the enzyme's activity. Highly refined structures have been deduced for the complexes between trypanosomal triosephosphate isomerase and a substrate analogue (glycerol-3-phosphate to 2.2 A), a transition state analogue (3-phosphonopropionic acid to 2.6 A), and a compound structurally related to both (3-phosphoglycerate to 2.2 A). The active site structures of these complexes were compared with each other, and with two previously determined structures of triosephosphate isomerase either free from inhibitor or complexed with sulfate. The comparison reveals three conformations available to the "flexible loop" near the active site of triosephosphate isomerase: open (no ligand), almost closed (sulfate), and fully closed (phosphate/phosphonate complexes). Also seen to be sensitive to the nature of the active site ligand is the catalytic residue Glu-167. The side chain of this residue occupies one of two discrete conformations in each of the structures so far observed. A "swung out" conformation unsuitable for catalysis is observed when sulfate, 3-phosphoglycerate, or no ligand is bound, while a "swung in" conformation ideal for catalysis is observed in the complexes with glycerol-3-phosphate or 3-phosphonopropionate. The water structure of the active site is different in all five structures. The results are discussed with respect to the triosephosphate isomerase structure function relationship, and with respect to an on-going drug design project aimed at the selective inhibition of glycolytic enzymes of T. brucei.
来自布氏布氏锥虫的磷酸丙糖异构酶晶体已被用于与该酶活性的三种竞争性抑制剂进行结合研究。已推导得到布氏锥虫磷酸丙糖异构酶与底物类似物（甘油 - 3 - 磷酸，分辨率为2.2 Å）、过渡态类似物（3 - 膦酰丙酸，分辨率为2.6 Å）以及与两者结构相关的化合物（3 - 磷酸甘油酸，分辨率为2.2 Å）形成的复合物的高度精确结构。将这些复合物的活性位点结构相互比较，并与之前测定的两种磷酸丙糖异构酶结构（一种无抑制剂，另一种与硫酸盐复合）进行比较。比较结果显示，磷酸丙糖异构酶活性位点附近的“柔性环”存在三种构象：开放（无配体）、几乎闭合（硫酸盐）和完全闭合（磷酸盐/膦酸盐复合物）。催化残基Glu - 167对活性位点配体的性质也很敏感。在迄今为止观察到的每个结构中，该残基的侧链占据两种离散构象之一。当结合硫酸盐、3 - 磷酸甘油酸或无配体时，观察到一种不利于催化的“摆动出”构象，而在与甘油 - 3 - 磷酸或3 - 膦酰丙酸形成的复合物中观察到一种有利于催化的“摆动入”构象。所有五种结构中活性位点的水结构都不同。本文针对磷酸丙糖异构酶的结构 - 功能关系以及旨在选择性抑制布氏锥虫糖酵解酶的正在进行的药物设计项目对这些结果进行了讨论。
