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Role of subunit interactions in P450 oligomers in the loss of homotropic cooperativity in the cytochrome P450 3A4 mutant L211F/D214E/F304W

机译:P450低聚物中亚基相互作用的作用在细胞色素P450 3A4突变体L211F / D214E / F304W的同质合作性丧失中

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摘要

The contribution of conformational heterogeneity to cooperativity in cytochrome P450 3A4 was investigated using the mutant L211F/D214E/F304W. Initial spectral studies revealed a loss of cooperativity of the 1-pyrenebutanol (1-PB) induced spin shift (S50 = 5.4 μM, n = 1.0) but retained cooperativity of α-naphthoflavone binding. Continuous variation (Job’s titration) experiments showed the existence of two pools of enzyme with different 1-PB binding characteristics. Monitoring of 1-PB binding by fluorescence resonance energy transfer from the substrate to the heme confirmed that the high affinity site (KD = 0.3 μM) is retained in at least some fraction of the enzyme, although cooperativity is masked. Removal of apoprotein on a second column increased the high spin content and restored cooperativity of 1-PB binding and of progesterone and testosterone 6β-hydroxylation. The loss of cooperativity in the mutant is, therefore, mediated by the interaction of holo- and apo-P450 in mixed oligomers.
机译:使用突变体L211F / D214E / F304W,研究了构象异质性对细胞色素P450 3A4中协同作用的贡献。最初的光谱研究显示,1-丁烯丁醇(1-PB)引起的自旋位移失去了协同作用(S50 = 5.4μM,n = 1.0),但保留了α-萘黄酮结合的协同作用。连续变化(乔布氏滴定法)实验表明,存在两种具有不同的1-PB结合特性的酶。通过荧光共振能量从底物转移到血红素来监测1-PB结合,证实了高亲和力位点(KD = 0.3μM)保留在酶的至少一部分中,尽管掩盖了协同作用。在第二根色谱柱上去除载脂蛋白增加了高旋转含量,并恢复了1-PB结合以及孕酮和睾丸激素6β-羟基化的协同作用。因此,突变体中协同性的丧失是由混合寡聚体中的holo-和apo-P450的相互作用介导的。

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