Effects of a naturally occurring compatible osmolyte on the internal dynamics of ribonuclease A.
Effects of a naturally occurring compatible osmolyte on the internal dynamics of ribonuclease A.
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DOI：
10.1021/bi00046a016
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发表时间：
1995-11
期刊：
影响因子：
2.9
通讯作者：
A. Wang;A. D. Robertson;D. W. Bolen
中科院分区：
文献类型：
--
作者：
A. Wang;A. D. Robertson;D. W. Bolen
渗透压调节剂是许多生物体在适应环境胁迫时在细胞内积累的小分子有机溶质。相容性渗透剂是渗透剂的一种功能性类别，其增加蛋白质稳定性，同时对蛋白质功能具有很少或没有影响。为了研究蛋白质稳定性、功能和内部动力学之间的相互关系，建立了氢交换（HX）猝灭方法，并用于研究蔗糖（一种典型的相容性渗透剂）对核糖核酸酶A结构波动的影响.结果发现，具有中间速率的酰胺质子的HX速率不受1 M蔗糖的影响，但缓慢交换的酰胺质子在1 M蔗糖中交换甚至更慢。慢交换质子的保护因子范围较窄，而中间交换质子的保护因子变化较大。与双过程模型一致[Woodward，C.K.，和希尔顿，B。D. 04 The Dog of the Woman（1980）J. 32，561-575]，我们得出结论，对于那些缓慢交换的酰胺质子，交换主要发生在蛋白质的紧凑的未折叠态系综。导致缓慢交换的内部动力学涉及暴露大的蛋白质表面积，类似于蛋白质解折叠时发生的情况。因为蔗糖反对蛋白质表面积暴露的这种增加，所以缓慢的HX速率和蛋白质稳定性都受到蔗糖的影响。对于那些酰胺质子与快速和中间HX率，交换主要发生从蛋白质的天然状态合奏。在交换所涉及的内部动态是本地化的表面积没有太大的变化，功能上重要的结构波动可能会发生在这个动态范围内。（250字处删节）
Osmolytes are small organic solutes accumulated intracellularly by many organisms as they adapt to environmental stresses. Compatible osmolytes, a functional class of osmolytes, increase protein stability while having little or no effect on protein function. To investigate the interrelationships between protein stability, function, and internal dynamics, a hydrogen exchange (HX) quench method was established and used to study the effects of sucrose (a typical compatible osmolyte) on the structural fluctuations of ribonuclease A. It was found that the HX rates of the amide protons with intermediate rates are not affected by 1 M sucrose, but the slow-exchanging amide protons exchange even slower in 1 M sucrose. The protection factors of the slow-exchanging protons fall into a comparatively narrow range while those of the intermediate-exchanging protons vary widely. In agreement with the two-process model [Woodward, C.K., & Hilton, B. D. (1980) Biophys. J. 32, 561-575], we conclude that for those slow-exchanging amide protons, the exchange occurs mainly from the compact unfolded state ensemble of the protein. The internal dynamics leading to slow exchange involve exposure of large protein surface areas, similar to that which occurs upon the unfolding of protein. Because sucrose opposes such an increase in protein surface area exposure, both the slow HX rates and the protein stability are affected by sucrose. For those amide protons with fast and intermediate HX rates, the exchange occurs mainly from the native state ensemble of the protein. The internal dynamics involved in the exchange are localized without much surface area change, and functionally important structural fluctuations are likely to occur within this dynamic range.(ABSTRACT TRUNCATED AT 250 WORDS)