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首页> 外文期刊>Biochemistry >Magnetic circular dichroism used to examine the interaction of Escherichia coli cytochrome bd with ligands.
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Magnetic circular dichroism used to examine the interaction of Escherichia coli cytochrome bd with ligands.

机译：磁性圆二色性用于检查大肠杆菌细胞色素bd与配体的相互作用。

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摘要

The interactions of the fully reduced and fully oxidized cytochrome bd from E. coli with ligands CO, NO, and CN- have been studied by a combination of absorption and magnetic circular dichroism (MCD) spectroscopy. In the reduced cytochrome bd, MCD resolves individual bands due to the high-spin heme b595 and the low-spin heme b558 components of the enzyme, allowing one to separately monitor their interactions along with ligand binding to the heme d component. The data show that at low concentrations, the ligands bind almost exclusively to heme d. At high concentrations, the ligands begin to interact with the low-spin heme b558. At the same time, no evidence for significant binding of the ligands to the high-spin heme b595 is revealed in either the reduced or the fully oxidized cytochrome bd complex. The data support the model [Borisov, V. B., Gennis, R. B., and Konstantinov, A. A. (1995) Biochemistry (Moscow) 60, 231-239] according to which the two high-spin hemes d and b595 share a high-affinity ligand binding site with a capacity for only a single molecule of the ligand; i.e., there is a strong negative cooperativity with respect to ligand binding to these two hemes with cytochrome d having an intrinsic ligand affinity much higher than that of heme b595.
机译：结合吸收和磁性圆二色性（MCD）光谱研究了大肠杆菌中完全还原和完全氧化的细胞色素bd与配体CO，NO和CN-的相互作用。在还原的细胞色素bd中，MCD分解了条带，这是由于酶的高纺丝血红素b595和低纺丝血红素b558组成，从而使人们可以分别监测它们的相互作用以及与血红素d组分结合的配体。数据表明，在低浓度下，配体几乎只与血红素d结合。在高浓度下，配体开始与低旋血红素b558相互作用。同时，在还原的或完全氧化的细胞色素bd复合物中，没有发现配体与高自旋血红素b595显着结合的证据。数据支持模型[Borisov，VB，Gennis，RB，and Konstantinov，AA（1995）Biochemistry（Moscow）60，231-239），根据该模型，两个高自旋血红素d和b595共享高亲和力配体结合仅能容纳单个配体分子的位点;即，与具有固有配体亲和力比血红素b595的亲和力高得多的细胞色素d的配体结合到这两个血红素上有很强的负协同性。

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