Entropy-driven binding of picomolar transition state analogue inhibitors to human 5'-methylthioadenosine phosphorylase.
Entropy-driven binding of picomolar transition state analogue inhibitors to human 5'-methylthioadenosine phosphorylase.
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DOI：
10.1021/bi201321x
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发表时间：
2011-11-29
期刊：
影响因子：
2.9
通讯作者：
Schramm, Vern L.
中科院分区：
文献类型：
--
作者：
Guan, Rong;Ho, Meng-Chiao;Brenowitz, Michael;Tyler, Peter C.;Evans, Gary B.;Almo, Steven C.;Schramm, Vern L.
人5‘-甲硫基腺苷磷酸化酶连接多胺生物合成和S-腺苷-L-蛋氨酸挽救途径，是抗癌药物的靶点。P-Cl-PHT-DADMe-IMMA是一种10 PM起效的紧束缚过渡态类似酶抑制剂。用该阻滞剂滴定均三聚体MTAP，确定了三个催化部位的等量结合和独立催化作用。对MTAP与紧密结合缓蚀剂的热力学分析表明，熵驱动的相互作用具有较小的热罚。缓蚀剂与−结合后，MTAP600cal/mol.K出现较大的负热变化，这与疏水作用的丧失和水的释放是一致的。分别在1.9A和2.0A分辨率下测定了apo-MTAP和MTAP与p-Cl-PHT-DADMe-IMMA络合物的晶体结构。抑制剂结合引起酶活性部位的缩合、三聚体界面的重组、活性部位和亚单位界面的水释放以及三聚体结构的紧凑。这些结构变化导致过渡态类似物的熵有利结合。将同源三聚体人MTAP与结构上相关的同源三聚体人嘌呤核苷磷酸化酶进行对比。P-Cl-Pat-DADMe-IMMA与MTAP的结合包含了17.6kcal/−的有利熵项和2.6kcal/mo1的不利热项。相反，8.5 Pm过渡态类似物与人PNP的结合表现出相反的行为，其不利的熵项为3.5kcal/m ol，有利的热项为−18.6kcal/m o l。过渡态类似物的相互作用反映了过渡态附近的蛋白质结构，MTAP和PNP在热力学上的巨大差异表明，蛋白质结构对催化的贡献存在显着差异。
Human 5′-methylthioadenosine phosphorylase (MTAP) links the polyamine biosynthetic and S-adenosyl-L-methionine salvage pathways and is a target for anticancer drugs. p-Cl-PhT-DADMe-ImmA is a 10 pM, slow-onset tight-binding transition state analogue inhibitor of the enzyme. Titration of homotrimeric MTAP with this inhibitor established equivalent binding and independent catalytic function of the three catalytic sites. Thermodynamic analysis of MTAP with tight-binding inhibitors revealed entropic-driven interactions with small enthalpic penalties. A large negative heat capacity change of −600 cal/mol•K upon inhibitor binding to MTAP is consistent with the loss of hydrophobic interactions and release of water. Crystal structures of apo MTAP and MTAP in complex with p-Cl-PhT-DADMe-ImmA were determined at 1.9 A and 2.0 A resolution, respectively. Inhibitor binding caused condensation of the enzyme active site, reorganization at the trimer interfaces, the release of water from the active sites and subunit interfaces, and compaction of the trimeric structure. These structural changes cause the entropy-favored binding of transition state analogues. Homotrimeric human MTAP is contrasted to the structurally related homotrimeric human purine nucleoside phosphorylase. p-Cl-PhT-DADMe- ImmA binding to MTAP involves a favorable entropy term of −17.6 kcal/mol with unfavorable enthalpy of 2.6 kcal/mol. In contrast, binding of an 8.5 pM transition state analogue to human PNP has been shown to exhibit the opposite behavior, with an unfavorable entropy term of 3.5 kcal/mol and a favorable enthalpy of −18.6 kcal/mol. Transition state analogue interactions reflect protein architecture near the transition state and the profound thermodynamic differences for MTAP and PNP suggest dramatic differences in contributions to catalysis from protein architecture.
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影响因子：
7.3
作者：
Evans, GB;Furneaux, RH;Tyler, PC
通讯作者：
Tyler, PC
DOI：
10.1107/s0907444904019158
发表时间：
2004-12-01
影响因子：
2.2
作者：
Emsley, P;Cowtan, K
通讯作者：
Cowtan, K
影响因子：
4.8
作者：
Basu, Indranil;Locker, Joseph;Schramm, Vern L.
通讯作者：
Schramm, Vern L.
影响因子：
2.9
作者：
Niedzwiecka, A;Stepinski, J;Stolarski, R
通讯作者：
Stolarski, R
影响因子：
2.9
作者：
Edwards, Achelle A.;Mason, Jennifer M.;Schramm, Vern L.
通讯作者：
Schramm, Vern L.