Structural characterization of the Redox-Dependent differences in the Cytochrome P450cam-Putidaredoxin Complex using solution NMR spectroscopy

Complexation between proteins as part of biological electron transfer reactions is driven by precise interactions that are often characterized by short lifetimes, weak affinities and high turnover rates. These complex interactions are difficult to study structurally in physiologically relevant oxidation states due to their transient nature and/or large molecular sizes. One such protein complex in the cytochrome P450 family of enzymes that is of great interest to researchers due to its prototypical nature is the Putidaredoxin (Pdx)- cytochrome P450cam (CYP101) electron transfer complex that is involved in hydroxylation of D-camphor in the bacterium Pseudomonas putida. While the individual protein structures for Pdx and CYP101 have been known for several years in both oxidized and reduced states, high-resolution structural information for the Pdx-CYP101 complex is still lacking in either oxidation state. This structural information is critical to not only determine the electron transfer pathway between the two proteins in this complex, but also to explain the role of Pdx as an effector in substrate turnover.

In this study, a solution NMR approach utilizing long-range distance restraints derived from paramagnetic relaxation effects is used to obtain structures of the Pdx-CYP101 complex in both substrate-bound oxidized and a catalytically competent reduced form. Key redox-dependent structural and dynamic differences between the two complexes have been characterized which provide insights into the mechanism of effector activity of Pdx.