Conformational substates in azurin.
Conformational substates in azurin.
复制标题
天青蛋白的构象亚态。
DOI：
10.1073/pnas.89.20.9681
复制
发表时间：
1992
影响因子：
11.1
通讯作者：
Nienhaus,GU
中科院分区：
文献类型：
--
作者：
Ehrenstein,D;Nienhaus,GU
天青蛋白是细菌电子传递链上的一种蓝色小铜蛋白。它在低温下与一氧化氮（NO）形成光不稳定复合物。在较宽的温度（80-280 K）和时间（10（-6）-10（2）s）范围内研究了配体结合平衡的温度依赖性和光解后的缔合反应动力学。低于200 K的非指数再结合是独立的NO浓度，被解释为内部重组。通过使用6.3 x 10（8）s-1的单个指前因子和以23 kJ/mol为中心、宽度为11 kJ/mol的焓垒的高斯分布，可以用阿克里尼乌斯定律来模拟再结合。在200 K以上，出现较慢的指数再结合过程。动力学对NO浓度的依赖性的特点是该反应为双分子再结合。NO与天青蛋白的结合动力学与一氧化碳与肌红蛋白的结合动力学具有令人印象深刻的相似性。我们的结论是，构象亚态不仅存在于血红素蛋白中，而且存在于具有不同活性位点和二级结构的蛋白质中。
Azurin is a small blue copper protein in the electron transfer chain of denitrifying bacteria. It forms a photolabile complex with nitric oxide (NO) at low temperatures. We studied the temperature dependence of the ligand binding equilibrium and the kinetics of the association reaction after photodissociation over a wide range of temperature (80-280 K) and time (10(-6)-10(2) s). The nonexponential rebinding below 200 K is independent of the NO concentration and is interpreted as internal recombination. The rebinding can be modeled with the Arrhenius law by using a single preexponential factor of 6.3 x 10(8) s-1 and a Gaussian distribution of enthalpy barriers centered at 23 kJ/mol with a width of 11 kJ/mol. Above 200 K, a slower, exponential rebinding process appears. The dependence of the kinetics on the NO concentration characterizes this reaction as bimolecular rebinding. The binding kinetics of NO to azurin show impressive analogies to the binding of carbon monoxide to myoglobin. We conclude that conformational substates occur not only in heme proteins but also in proteins with different active sites and secondary structures.