Fig. 7: Conformational changes in DPOR.
From: Cryo-EM captures the coordination of asymmetric electron transfer through a di-copper site in DPOR
A A superposition of the NB-protein from the three cryo-EM structures (apo, Pchlide-bound, and under single-turnover) is shown, and the key residues, the [4Fe-4S]NB cluster, and the di-Cu site are depicted. Overall changes in the environment surrounding the substrate and clusters are visible, and asymmetric motions are observed between the two halves of the NB-protein. The residues are colored to match the individual NB-protein subunits and shaded to correspond to the NB-protein apo (light), Pchlide-bound NB-protein (medium), and DPOR turnover (dark) structures. Residues colored pink, blue, purple, and green represent BchN, BchB, BchN′, and BchB′, respectively. The * denotes residues that interact across the two halves in trans. We propose that the transfer of an electron in the left half of the NB-protein (bound to L-protein) is promoted due to the proper alignment of residues that favor ET. These residues are not aligned in the other half leading to the allosteric suppression of L-protein binding and conditions that do not favor ET. B Superposition of two NB-protein halves in the DPOR-turnover structure. Select amino acids that show conformational changes between the two halves are shown. Asp-374 (red) and the C17 = C18 double bond in Pchlide (green) are highlighted. Distances between the di-Cu cluster and the C17 = C18 bond (and His-378) and the [4Fe-4S]NB cluster are shown. The blue and pink arrows denote speculative paths of electron transfer from the [4Fe-4S]NB to Pchlide.
