Conformational dependence of hemoglobin reactivity under high viscosity conditions: The role of solvent slaved dynamics
Conformational dependence of hemoglobin reactivity under high viscosity conditions: The role of solvent slaved dynamics
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DOI：
10.1021/ja072342b
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发表时间：
2007-10-24
影响因子：
15
通讯作者：
Friedman, Joel M.
中科院分区：
文献类型：
--
作者：
Samuni, Uri;Roche, Camille J.;Friedman, Joel M.
引入了蛋白质动态状态的概念。这个概念是基于(i)相对于溶剂奴役的蛋白质动力学被分层组织和（ii）在给定测量的时间窗口内哪一层动力学是有效的。利用蛋白质动态状态的概念分析了一氧化碳溶胶-凝胶包膜人血红蛋白（HbA）的动力学相，并选择了重组突变体。温度相关的测量是在非常高的粘度条件下进行的，通过将样品浸泡在过量的甘油中获得。结果与给定的溶剂从属动力学层在主要依赖于溶剂和温度的时间延迟（相对于测量的开始）开始工作相一致。然而，动力学的功能结果是蛋白质和构象特异性的。平衡种群和捕获的变构中间体的动力学痕迹显示出一致的进展，揭示了构象和水合作用在反应性控制中的作用。铁锌对称杂化形式的HbA被用来显示T态a和β亚基的动力学模式之间的巨大差异。总体结果支持一个HbA变构模型，其中配体结合诱导的从脱氧T态到高亲和R态的转变通过一系列T态中间体进行。
The concept of protein dynamic states is introduced. This concept is based on (i) protein dynamics being organized hierarchically with respect to solvent slaving and (ii) which tier of dynamics is operative over the time window of a given measurement. The protein dynamic state concept is used to analyze the kinetic phases derived from the recombination of carbon monoxide to sol-gel-encapsulated human adult hemoglobin (HbA) and select recombinant mutants. The temperature-dependent measurements are made under very high viscosity conditions obtained by bathing the samples in an excess of glycerol. The results are consistent with a given tier of solvent slaved dynamics becoming operative at a time delay (with respect to the onset of the measurement) that is primarily solvent- and temperature-dependent. However, the functional consequences of the dynamics are protein- and conformation-specific. The kinetic traces from both equilibrium populations and trapped allosteric intermediates show a consistent progression that exposes the role of both conformation and hydration in the control of reactivity. Iron-zinc symmetric hybrid forms of HbA are used to show the dramatic difference between the kinetic patterns for T state a and beta subunits. The overall results support a model for allostery in HbA in which the ligand-binding-induced transition from the deoxy T state to the high -affinity R state proceeds through a progression of T state intermediates.