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首页> 外文期刊>Journal of Molecular Biology >Crystal structure of a truncated mutant of glucose-fructose oxidoreductase shows that an N-terminal arm controls tetramer formation
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Crystal structure of a truncated mutant of glucose-fructose oxidoreductase shows that an N-terminal arm controls tetramer formation

机译：葡萄糖-果糖氧化还原酶的截短突变体的晶体结构表明，N末端臂控制四聚体的形成

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摘要

N-terminal or C-terminal arms that extend from folded protein domains can play a critical role in quaternary structure and other intermolecular associations and/or in controlling biological activity. We have tested the role of an extended N-terminal arm in the structure and function of a periplasmic enzyme glucose-fructose oxidoreductase (GFOR) from Zymomonas mobilis. We have determined the crystal structure of the NAD(+) complex of a truncated form of the enzyme, GFOR Delta, in which the first 22 residues of the N-terminal arm of the mature protein have been deleted. The structure, refined at 2.7 Angstrom resolution (R-cryst = 24.1%, R-free = 28.4%), shows that the truncated form of the enzyme forms a dimer and implies that the N-terminal arm is essential for tetramer formation by wild-type GFOR. Truncation of the N-terminal arm also greatly increases the solvent exposure of the cofactor; since GFOR activity is dependent on retention of the cofactor during the catalytic cycle we conclude that the absence of GFOR activity in this mutant results from dissociation of the cofactor. The N-terminal arm thus determines the quaternary structure and the retention of the cofactor for GFOR activity and during translocation into the periplasm. The structure of GFOR Delta also shows how an additional mutation, Ser64Asp, converts the strict NADP(+) specificity of wild-type GFOR to a dual NADP(+)/NAD(+) specificity. (C) 2000 Academic Press. [References: 32]
机译：从折叠的蛋白质结构域延伸的N末端或C末端臂在四级结构和其他分子间缔合和/或控制生物活性中起关键作用。我们已经测试了运动的发酵单胞菌周质酶葡萄糖-果糖氧化还原酶（GFOR）的延伸的N末端臂的结构和功能中的作用。我们已经确定了截短形式的酶GFOR Delta的NAD（+）复合物的晶体结构，其中成熟蛋白N末端臂的前22个残基已被删除。以2.7埃的分辨率精炼的结构（R-晶体= 24.1％，无R = 28.4％），表明该酶的截短形式形成了一个二聚体，并暗示了N末端臂对于野生形成四聚体至关重要。型GFOR。 N末端臂的截短也大大增加了辅因子的溶剂暴露量。由于GFOR活性取决于催化循环中辅因子的保留，因此我们得出结论，该突变体中GFOR活性的缺乏是辅因子解离的结果。因此，N末端臂决定了GFOR活性以及在易位进入周质期间的四级结构和辅因子的保留。 GFOR Delta的结构还显示了另一个突变Ser64Asp如何将野生型GFOR的严格NADP（+）特异性转化为双重NADP（+）/ NAD（+）特异性。 （C）2000学术出版社。 [参考：32]

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