Borisov V B
Department of Molecular Energetics of Microorganisms, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.
Biochemistry (Mosc). 2008 Jan;73(1):14-22. doi: 10.1134/s0006297908010021.
Comparative studies on the interaction of the membrane-bound and detergent-solubilized forms of the enzyme in the fully reduced state with carbon monoxide at room temperature have been carried out. CO brings about a bathochromic shift of the heme d band with a maximum at 644 nm and a minimum at 624 nm, and a peak at 540 nm. In the Soret band, CO binding to cytochrome bd results in absorption decrease and minima at 430 and 445 nm. Absorption perturbations in the Soret band and at 540 nm occur in parallel with the changes at 630 nm and reach saturation at 3-5 microM CO. The peak at 540 nm is probably either beta-band of the heme d-CO complex or part of its split alpha-band. In both forms of cytochrome bd, CO reacts predominantly with heme d. Addition of high CO concentrations to the solubilized cytochrome bd results in additional spectral changes in the gamma-band attributable to the reaction of the ligand with 10-15% of low-spin heme b558. High-spin heme b595 does not bind CO even at high concentrations of the ligand. The apparent dissociation constant values for the heme d-CO complex of the membrane-bound and detergent-solubilized forms of the fully reduced enzyme are about 70 and 80 nM, respectively.
已经对完全还原状态下的膜结合形式和去污剂增溶形式的酶在室温下与一氧化碳的相互作用进行了比较研究。一氧化碳使血红素d带发生红移，在644nm处有最大值，在624nm处有最小值，在540nm处有一个峰。在索雷特带中，一氧化碳与细胞色素bd结合导致吸收减少，在430和445nm处有最小值。索雷特带和540nm处的吸收扰动与630nm处的变化同时发生，并在3-5μM一氧化碳时达到饱和。540nm处的峰可能是血红素d-一氧化碳复合物的β带或其分裂的α带的一部分。在细胞色素bd的两种形式中，一氧化碳主要与血红素d反应。向增溶的细胞色素bd中加入高浓度的一氧化碳会导致γ带出现额外的光谱变化，这归因于配体与10-15%的低自旋血红素b558反应。即使在高浓度配体存在下，高自旋血红素b595也不结合一氧化碳。完全还原酶的膜结合形式和去污剂增溶形式的血红素d-一氧化碳复合物的表观解离常数分别约为70和80 nM。
