Welch W, Ahmad S, Airey J A, Gerzon K, Humerickhouse R A, Besch H R, Ruest L, Deslongchamps P, Sutko J L
Department of Biochemistry, University of Nevada, Reno 89557.
Biochemistry. 1994 May 24;33(20):6074-85. doi: 10.1021/bi00186a006.
Ryanodine binds to specific membrane proteins, altering the calcium permeability of intracellular membranes. In this study 19 ryanoids were isolated or synthesized and the structures correlated to the strength of binding to vertebrate skeletal muscle ryanodine receptors. Global minima were determined by employment of molecular mechanics and dynamics augmented by systematic searching of conformational space. Overall, steric and electrostatic factors contribute about equally to the differences in the experimentally determined dissociation constants. The dominant electrostatic interaction is localized to a hydroxyl group in an apolar region of the molecule. The pyrrole and isopropyl groups located together at one pole of the molecule have the greatest effect on steric interactions between ligand and receptor. We suggest ryanodine binds to the receptor with the pyrrole and isopropyl groups buried deep inside a cleft in the protein. This arrangement places special importance on the conformation of the pyrrole and isopropyl groups. In contrast, the opposite pole appears to be positioned at the entrance of the binding pocket because bulky adducts placed in the 9 position of ryanodine alter binding minimally. For example, a fluorescent ryanodine adduct was synthesized which has a dissociation constant close to that of ryanodine. Detailed examination reveals subtle interactions between ryanoid and receptor. In many cases, the major factors altering the strength of binding were found to be conformational alterations in the molecule remote from the site of covalent modification.
雷诺丁与特定的膜蛋白结合，改变细胞内膜的钙通透性。在本研究中，分离或合成了19种雷诺类化合物，并将其结构与它们与脊椎动物骨骼肌雷诺丁受体的结合强度进行关联。通过分子力学和动力学方法，并辅以对构象空间的系统搜索来确定全局最小值。总体而言，空间因素和静电因素对实验测定的解离常数差异的贡献大致相同。主要的静电相互作用定位于分子非极性区域的一个羟基上。位于分子同一极的吡咯基和异丙基对配体与受体之间的空间相互作用影响最大。我们认为雷诺丁与受体结合时，吡咯基和异丙基深埋在蛋白质的一个裂隙中。这种排列使得吡咯基和异丙基的构象尤为重要。相比之下，相反的一极似乎位于结合口袋的入口处，因为置于雷诺丁9位的庞大加合物对结合的影响最小。例如，合成了一种荧光雷诺丁加合物，其解离常数与雷诺丁相近。详细研究揭示了雷诺类化合物与受体之间的微妙相互作用。在许多情况下，发现改变结合强度的主要因素是分子中远离共价修饰位点处的构象变化。
