Schlichting I, Berendzen J, Phillips G N, Sweet R M
Department of Biophysics, Max Planck Institute for Medical Research, Heidelberg, Germany.
Nature. 1994 Oct 27;371(6500):808-12. doi: 10.1038/371808a0.
Myoglobin is a globular haem protein that reversibly binds ligands such as O2 and CO. Single photons of visible light can break the covalent bond between CO and the haem iron in carbon-monoxy-myoglobin (MbCO) and thus form an unstable intermediate, MbCO, with the CO inside the protein. The ensuing rebinding process has been extensively studied as a model for the interplay of dynamics, structure and function in protein reactions. We have used X-ray crystallography at liquid-helium temperatures to determine the structure of MbCO to a resolution of 1.5 A. The photodissociated CO lies on top of the haem pyrrole ring C. Comparison with the CO-bound and unligated myoglobin structures reveals that on photodissociation of the CO, the haem 'domes', the iron moves partially out of the haem plane, the iron-proximal histidine bonds is compressed, the F helix is strained and the distal histidine swings towards the outside of the ligand-binding pocket.
肌红蛋白是一种球状血红素蛋白，可与诸如O2和CO等配体可逆结合。可见光的单个光子可打破一氧化碳肌红蛋白（MbCO）中CO与血红素铁之间的共价键，从而在蛋白质内部形成一个不稳定的中间体MbCO，其中CO仍在蛋白质内部。随后的重新结合过程作为蛋白质反应中动力学、结构和功能相互作用的模型已得到广泛研究。我们利用液氦温度下的X射线晶体学将MbCO的结构解析到了1.5埃的分辨率。光解离的CO位于血红素吡咯环C的上方。与结合CO和未结合配体的肌红蛋白结构相比，结果显示，CO发生光解离时，血红素“隆起”，铁部分移出血红素平面，铁近端组氨酸键被压缩，F螺旋受到拉伸，远端组氨酸向配体结合口袋外部摆动。
