Structural Basis of the Molecular Switch between Phosphatase and Mutase Functions of Human Phosphomannomutase 1 under Ischemic Conditions.
Structural Basis of the Molecular Switch between Phosphatase and Mutase Functions of Human Phosphomannomutase 1 under Ischemic Conditions.
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DOI：
10.1021/acs.biochem.8b00223
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发表时间：
2018-06-26
期刊：
影响因子：
2.9
通讯作者：
Allen, Karen N.
中科院分区：
文献类型：
--
作者：
Ji, Tianyang;Zhang, Chunchun;Zheng, Li;Dunaway-Mariano, Debra;Allen, Karen N.
人磷酸甘露糖变位酶PMM 1和PMM 2催化己糖6-磷酸和己糖1-磷酸的相互转化。这两种异构体共享66%的序列同一性，并在体外具有类似的动力学性质的突变酶，但在体内的功能作用不同。虽然PMM 2的生理作用是催化提供蛋白质糖基化所必需的甘露糖1-磷酸（Man-1-P）的磷酸化反应，但PMM 1被认为在肌苷一磷酸（IMP）存在下提供磷酸水解酶活性，将葡萄糖1，6-二磷酸（Glu-1，6-P2）转化为葡萄糖6-磷酸（Glu-6-P），在脑缺血期间拯救糖酵解。为了揭示IMP结合如何将PMM 1从β-磷酸酶转化为磷酸酶的结构基础，测定了与IMP复合的PMM 1的1.93 μ m分辨率结构。该结构显示IMP结合在底物募集位点，从而抑制β-内酰胺酶活性，同时激活磷酸酶水解产生的磷酸酶活性（IMP Kact = 1.5 μM）。结合的结构和定点突变证实，远程静电相互作用提供的Arg 180和Arg 183保守PMM 1的IMP结合的主要贡献者，和他们的oblation去除磷酸酶，但不去除磷酸酶活性。这些残基不存在于PMM 2亚型，因此缺乏显着的磷酸酶活性的IMP.T2弛豫NMR和SAXS的存在下，一起支持的假设，IMP结合PMM 1有利于酶的构象，是催化能力的水攻击在磷酰基中间体。这种机制可以推广到通过共价中间体起作用的其他酶。
The human phosphomannomutases PMM1 and PMM2 catalyze the interconversion of hexose 6-phosphates and hexose 1-phosphates. The two isoforms share 66% sequence identity and have similar kinetic properties as mutases in vitro, but differ in their functional roles in vivo. Though the physiological role of PMM2 is catalysis of the mutase reaction that provides the mannose 1-phosphate (Man-1-P) essential for protein glycosylation, PMM1 is thought to provide a phosphohydrolase activity in the presence of inosine monophosphate (IMP), converting glucose 1,6-bisphosphate (Glu-1,6-P2) to glucose 6-phosphate (Glu-6-P), rescuing glycolysis during brain ischemia. To uncover the structural basis of how IMP binding converts PMM1 from a mutase to a phosphatase, the 1.93 Å resolution structure of PMM1 complexed with IMP was determined. The structure reveals IMP bound at the substrate recruitment site, thus inhibiting the mutase activity while simultaneous activating a phosphatase activity (IMP Kact = 1.5 μM) resulting from the hydrolysis of the phospho-enzyme. The bound structure and site-directed mutagenesis confirm that the long-range electrostatic interactions provided by Arg180 and Arg183 conserved in PMM1 are the major contributors to IMP binding, and their oblation removes phosphatase but not mutase activity. These residues are not present in the PMM2 isoform, which consequently lacks significant phosphatase activity in the presence of IMP. T2 relaxation NMR and SAXS together support the hypothesis that IMP binding to PMM1 favors an enzyme conformation that is catalytically competent for water attack at the phosphoaspartyl intermediate. Such a mechanism may be generalizable to other enzymes that act through covalent intermediates.
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影响因子：
2.9
作者：
Dai, Jianying;Finci, Lorenzo;Zhang, Chunchun;Lahiri, Sushmita;Zhang, Guofeng;Peisach, Ezra;Allen, Karen N.;Dunaway-Mariano, Debra
通讯作者：
Dunaway-Mariano, Debra
影响因子：
2.9
作者：
Huang, Hua;Patskovsky, Yury;Dunaway-Mariano, Debra
通讯作者：
Dunaway-Mariano, Debra
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：
6.1
作者：
Konarev, PV;Volkov, VV;Svergun, DI
通讯作者：
Svergun, DI
影响因子：
2
作者：
Dalvit, Claudio;Gossert, Alvar D.;Piotto, Martial
通讯作者：
Piotto, Martial