Two-dimensional correlation spectroscopy reveals coupled immunoglobulin regions of differential flexibility that influence stability.
Two-dimensional correlation spectroscopy reveals coupled immunoglobulin regions of differential flexibility that influence stability.
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DOI：
10.1021/bi700645k
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发表时间：
2007-08
期刊：
影响因子：
2.9
通讯作者：
Tim J. Kamerzell;C. Middaugh
中科院分区：
文献类型：
--
作者：
Tim J. Kamerzell;C. Middaugh
尽管公认的重要性，蛋白质的灵活性和动态的分子识别和构象稳定性，我们对这些关系的理解是不完整的。免疫球蛋白的灵活性对于抗原结合和适应不同的分子形状和大小是必不可少的。免疫球蛋白的固有柔性也使得这些分子适合于研究蛋白质柔性和稳定性之间的可能关系。为了更好地理解这些相互关系，我们采用广义扰动为基础的二维相关FTIR光谱监测的时间演变的H-D交换的IgG 1作为pH值的函数。不同的免疫球蛋白区域的差异灵活性描述在响应外部扰动，并显示变化很大。在pH值为6时，汇率有差别、因而灵活性也有差别的区域数量最多。分别在pH 6、8、4和2下观察到大约7、6、5和4种以不同速率交换的独立状态。根据酰胺I和酰胺II综合面积的衰减计算的汇率总体分布进一步证明了多个区域具有不同的灵活性。从异步振动模式确定的事件在pH 4的顺序是显着的兴趣，并建议质子化的Glu和Asp侧链首先发生，并启动不同的片和转弯结构的构象和灵活性的变化。不同区域柔性和构象耦合之间的复杂相互关系（即，协同性）影响该IgG的稳定性。
Despite the well-accepted importance of protein flexibility and dynamics in molecular recognition and conformational stability, our understanding of these relationships is incomplete. Immunoglobulin flexibility is essential for antigen binding and adaptation to diverse molecular shapes and sizes. The inherent flexibility of immunoglobulins also renders these molecules suitable for investigating the possible relationships between protein flexibility and stability. To better understand these inter-relationships, we employ generalized perturbation-based two-dimensional correlation FTIR spectroscopy to monitor the time evolution of H-D exchange of an IgG1 as a function of pH. The differential flexibility of various immunoglobulin regions is described in response to an external perturbation and shown to vary widely. The greatest number of regions with differential exchange rates and, thus differential flexibility, is seen at pH 6. Approximately seven, six, five, and four separate states that exchange with different rates were observed at pH 6, 8, 4, and 2, respectively. The overall distribution of exchange rates calculated from the decays of the integrated Amide I and Amide II areas provides further evidence of multiple regions with differential flexibility. The sequence of events at pH 4 determined from the asynchronous vibrational patterns is of significant interest and suggests protonation of Glu and Asp side chains occurs first and initiates changes in the conformation and flexibility of different sheet and turns structure. A complex inter-relationship between differential regional flexibility and conformational coupling (i.e., cooperativity) initiated by changes in pH influences the stability of this IgG.