Loop Interactions during Catalysis by Dihydrofolate Reductase from Moritella profunda
Loop Interactions during Catalysis by Dihydrofolate Reductase from Moritella profunda
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DOI：
10.1021/bi500508z
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发表时间：
2014-07-29
期刊：
影响因子：
2.9
通讯作者：
Allemann, Rudolf K.
中科院分区：
文献类型：
--
作者：
Behiry, Enas M.;Evans, Rhiannon M.;Allemann, Rudolf K.
二氢叶酸还原酶（Dihydrofolate reductase， DHFR）常被用作研究蛋白质动力学与催化作用关系的模型体系。我们研究了来自深海森氏菌（Moritella profunda, MpDHFR）的冷适应DHFR的许多变体，其中催化作用重要的M20和PG环已经改变，并与来自大肠杆菌（Escherichia coli, EcDHFR）的相应变体进行了比较。在两种酶的催化循环中，M20环的突变不影响氢化物从还原的烟酰胺腺嘌呤二核苷酸磷酸转移到底物7,8-二氢叶酸的实际化学步骤；它们影响EcDHFR的稳态周转率，但对MpDHFR没有影响。FG环的突变对两种DHFRs的催化作用也有不同的影响。尽管这两种酶在pH值为7时很可能共享一个共同的催化循环，但这些环的运动在EcDHFR中对催化循环的进展很重要，似乎在MpDHFR中不起重要作用
Dihydrofolate reductase (DHFR) is often used as a model system to study the relation between protein dynamics and catalysis. We have studied a number of variants of the cold-adapted DHFR from Moritella profunda (MpDHFR), in which the catalytically important M20 and PG loops have been altered, and present a comparison with the corresponding variants of the well-studied DHFR from Escherichia coli (EcDHFR). Mutations in the M20 loop do not affect the actual chemical step of transfer of hydride from reduced nicotinamide adenine dinucleotide phosphate to the substrate 7,8-dihydrofolate in the catalytic cycle in either enzyme; they affect the steady state turnover rate in EcDHFR but not in MpDHFR. Mutations in the FG loop also have different effects on catalysis by the two DHFRs. Despite the two enzymes most likely sharing a common catalytic cycle at pH 7, motions of these loops, known to be important for progression through the catalytic cycle in EcDHFR, appear not to play a significant role in MpDHFR