Movements of BSL and helices C/D induced by Pdx binding in MD structures. The BSL spin-label groups in the closed (camphor-bound, green), open (camphor-free, blue), and complex (camphor- and Pdf-bound, brown) states are shown as sticks. PdxW106 perturbed the BSL on helix C upon binding of Pdx, resulting in a significant BSL side-chain movement. Because P450cam in open and complex states has a similar open conformation, only the most representative structures of MD trajectories from cluster analysis in the closed and complex states are compared and shown as green and brown cartoons, respectively. The dashed lines indicate the BSL-AC and CD distances between nitroxide nitrogen atoms in closed, open, and complex states.