Salehi Seyedeh Maryam, Koner Debasish, Meuwly Markus
Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland.
J Phys Chem B. 2020 Dec 31;124(52):11882-11894. doi: 10.1021/acs.jpcb.0c08048. Epub 2020 Nov 27.
The infrared spectroscopy and dynamics of -CO labels in wild type and mutant insulin monomer and dimer are characterized from molecular dynamics simulations using validated force fields. It is found that the spectroscopy of monomeric and dimeric forms in the region of the amide-I vibration differs for residues B24-B26 and D24-D26, which are involved in dimerization of the hormone. Also, the spectroscopic signatures change for mutations at position B24 from phenylalanine, which is conserved in many organisms and is known to play a central role in insulin aggregation, to alanine or glycine. Using three different methods to determine the frequency trajectories (solving the nuclear Schrödinger equation on an effective 1-dimensional potential energy curve, using instantaneous normal modes, and using parametrized frequency maps) leads to the same overall conclusions. The spectroscopic response of monomeric WT and mutant insulin differs from that of their respective dimers, and the spectroscopy of the two monomers in the dimer is also not identical. For the WT and F24A and F24G monomers, spectroscopic shifts are found to be ∼20 cm for residues (B24-B26) located at the dimerization interface. Although the crystal structure of the dimer is that of a symmetric homodimer, dynamically the two monomers are not equivalent on the nanosecond time scale. Together with earlier work on the thermodynamic stability of the WT and the same mutants, it is concluded that combining computational and experimental infrared spectroscopy provides a potentially powerful way to characterize the aggregation state and dimerization energy of modified insulins.
利用经过验证的力场，通过分子动力学模拟对野生型和突变型胰岛素单体及二聚体中 -CO 标签的红外光谱和动力学进行了表征。研究发现，参与激素二聚化的 B24 - B26 和 D24 - D26 残基在酰胺 -I 振动区域的单体和二聚体形式的光谱有所不同。此外，B24 位的突变从许多生物体中保守且已知在胰岛素聚集中起核心作用的苯丙氨酸变为丙氨酸或甘氨酸时，光谱特征也会改变。使用三种不同方法确定频率轨迹（在有效的一维势能曲线上求解核薛定谔方程、使用瞬时简正模式以及使用参数化频率图）得出了相同的总体结论。野生型和突变型胰岛素单体的光谱响应与其各自二聚体的不同，并且二聚体中两个单体的光谱也不相同。对于野生型、F24A 和 F24G 单体，位于二聚化界面的（B24 - B26）残基的光谱位移约为 20 cm。尽管二聚体的晶体结构是对称同二聚体，但在纳秒时间尺度上，两个单体在动力学上并不等效。结合早期关于野生型和相同突变体的热力学稳定性的研究工作，可以得出结论，将计算红外光谱和实验红外光谱相结合为表征修饰胰岛素的聚集状态和二聚化能提供了一种潜在的有力方法。
