绑定核苷酸还原酶的变构效应物蛋白R1:减少活性部位半胱氨酸促进底物结合。
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埃里克森M Uhlin U, Ramaswamy年代,Ekberg M, Regnstrom K, Sjoberg BM,雷欧H
绑定核苷酸还原酶的变构效应物蛋白R1:减少活性部位半胱氨酸促进底物结合。
结构。1997年8月15日,5 (8):1077 - 92。
- PubMed ID
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9309223 (在PubMed]
- 文摘
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背景:核苷酸还原酶(RNR)是一种DNA合成的关键酶催化脱氧核苷酸从头合成。酶由两个二聚体,称为R1和R2,包含氧化还原活性半胱氨酸残基,Cys462 Cys225。核苷酸的还原脱氧核苷酸涉及自由基的转移。激进的途径曾被建议从结晶的结果,和支持定点诱变研究。大多数RNRs通过两种不同的变构调节nucleotide-binding网站:一个站点控制一般活动和其他控制底物特异性。我们的目标一直是结晶学证明衬底绑定和定位两个effector-binding网站。结果:我们报告RNR R1的第一晶体结构在降低形式。结构表明,经氧化还原活性降低半胱氨酸的硫原子Cys462变得深埋地下。更容易获得Cys225移动到前位置Cys462衬底腾出空间。此外,R1的复合物的结构效应,效应模拟和效应+衬底提供这些结合位点的信息。 The substrate GDP binds in a cleft between two domains with its beta-phosphate bound to the N termini of two helices; the ribose forms hydrogen bonds to conserved residues. Binding of dTTP at the allosteric substrate specificity site stabilizes three loops close to the dimer interface and the active site, whereas the general allosteric binding site is positioned far from the active site. CONCLUSIONS: Binding of substrate at the active site of the enzyme is structurally regulated in two ways: binding of the correct substrate is regulated by the binding of allosteric effectors and binding of the actual substrate occurs primarily when the active-site cysteines are reduced. One of the loops stabilized upon binding of dTTP participates in the formation of the substrate-binding site through direct interaction with the nucleotide base. The general allosteric effector site, located far from the active site, appears to regulate subunit interactions within the holoenzyme.