Structure of Physarum polycephalum cytochrome b₅ reductase at 1.56 Å resolution

Physarum polycephalum cytochrome b₅ reductase catalyzes the reduction of cytochrome b₅ by NADH. The structure of P. polycephalum cytochrome b₅ reductase was determined at a resolution of 1.56 Å. The molecular structure was compared with that of human cytochrome b₅ reductase, which had previously been determined at 1.75 Å resolution [Bando et al. (2004), Acta Cryst. D60, 1929–1934]. The high-resolution structure revealed conformational differences between the two enzymes in the adenosine moiety of the FAD, the lid region and the linker region. The structural properties of both proteins were inspected in terms of hydrogen bonding, ion pairs, accessible surface area and cavity volume. The differences in these structural properties between the two proteins were consistent with estimates of their thermostabilities obtained from differential scanning calorimetry data.