X-ray structure of domain I of the proton-pumping membrane protein transhydrogenase from Escherichia coli
X-ray structure of domain I of the proton-pumping membrane protein transhydrogenase from Escherichia coli
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DOI：
10.1016/j.jmb.2005.07.022
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发表时间：
2005-09-16
影响因子：
5.6
通讯作者：
Krengel, U
中科院分区：
文献类型：
--
作者：
Johansson, T;Oswald, C;Krengel, U
二聚体整体膜蛋白烟酰胺核苷酸转氢酶是线粒体和原核生物中NADPH细胞再生所必需的，用于解毒和生物合成目的。在生理条件下，转氢酶将NADH对NADP（+）的可逆还原与向内质子跨膜易位结合在一起。在这里，我们展示了来自大肠杆菌的转氢酶的NAD(H)结合域I的晶体结构，在没有以及在氧化和还原底物存在的情况下。在1.9-2.0埃分辨率下测定了结构。总的来说，这些结构与之前发表的红红螺旋藻转氢酶的NAD(H)结合结构域的晶体结构非常相似。然而，这个特殊的结构域是独一无二的，因为它是共价连接到转氢酶的整体膜部分。两种化合物结构之间的比较研究揭示了表面性质的巨大差异，并指出刚性肽（PAPP）在构象偶联的连接连接中可能具有重要作用。此外，对一个缺失突变体的动力学分析表明，该结构元素对催化活性很重要，但对结构域I：结构域III相互作用或二聚体形成并不重要。综上所述，这些结果对包括哺乳动物酶在内的大量转氢酶的酶机制具有重要意义，这些酶在结构域I和结构域II之间含有连接连接体。(c) 2005 Elsevier Ltd版权所有。
The dimeric integral membrane protein nicotinamide nucleotide transhydrogenase is required for cellular regeneration of NADPH in mitochondria and prokaryotes, for detoxification and biosynthesis purposes. Under physiological conditions, transhydrogenase couples the reversible reduction of NADP(+) by NADH to an inward proton translocation across the membrane. Here, we present crystal structures of the NAD(H)-binding domain I of transhydrogenase from Escherichia coli, in the absence as well as in the presence of oxidized and reduced substrate. The structures were determined at 1.9-2.0 angstrom resolution. Overall, the structures are highly similar to the crystal structure of a previously published NAD(H)-binding domain, from Rhodospirillum rubrum transhydrogenase. However, this particular domain is unique, since it is covalently connected to the integral-membrane part of transhydrogenase. Comparative studies between the structures of the two species reveal extensively differing surface properties and point to the possible importance of a rigid peptide (PAPP) in the connecting linker for conformational coupling. Further, the kinetic analysis of a deletion mutant, from which the protruding beta-hairpin was removed, indicates that this structural element is important for catalytic activity, but not for domain I:domain III interaction or dimer formation. Taken together, these results have important implications for the enzyme mechanism of the large group of transhydrogenases, including mammalian enzymes, which contain a connecting linker between domains I and II. (c) 2005 Elsevier Ltd. All rights reserved.