Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, USA.
Inorg Chem. 2009 Dec 21;48(24):11504-6. doi: 10.1021/ic9018376.
Density functional theory calculations were used to investigate the binding mode of copper(I) nitrosyl (Cu(I)-NO) in copper nitrite reductase (CuNIR). The end-on Cu(I)-NO geometry (2) was found to be the global energy minimum, while the side-on binding mode (1) corresponds to a local minimum. Isoleucine-257 severely interacts sterically with the Cu(I)-NO unit when bound end-on but not in the side-on case. In addition, the side-on geometry is also stabilized by a hydrogen bond between aspartic acid-98 and NO, estimated to be approximately 3 kcal/mol. The steric constraint of the CuNIR active site is mainly responsible for the observed side-on coordination of NO in the CuNIR crystal structure. We speculate that a small conformational change of the active site that slightly changes the position of isoleucine-257 would allow NO to bind end-on. This explains the observed end-on binding of NO to copper(I) when CuNIR is in solution.
密度泛函理论计算被用于研究亚硝酰铜（Cu(I)-NO）在铜亚硝酸盐还原酶（CuNIR）中的结合模式。端到端的 Cu(I)-NO 几何结构（2）被发现是全局能量最低点，而侧接结合模式（1）对应于局部最低点。当结合端到端时，异亮氨酸-257 与 Cu(I)-NO 单元严重相互作用，但在侧接情况下则不然。此外，侧接几何结构还通过天冬氨酸-98 和 NO 之间的氢键稳定，估计约为 3 千卡/摩尔。CuNIR 活性位点的空间位阻主要负责观察到的 NO 在 CuNIR 晶体结构中的侧接配位。我们推测，活性位点的微小构象变化会稍微改变异亮氨酸-257 的位置，从而允许 NO 端到端结合。这解释了在溶液中 CuNIR 时观察到的 NO 与铜（I）的端到端结合。
