Crystal structure of the FMN‐binding domain of human cytochrome P450 reductase at 1.93 Å resolution

Abstract

The crystal structure of the FMN-binding domain of human NADPH-cytochrome P450 reductase (P450R-FMN), a key component in the cytochrome P450 monooxygenase system, has been determined to 1.93 A resolution and shown to be very similar both to the global fold in solution (Barsukov I et al., 1997, J Biomol NMR 10:63-75) and to the corresponding domain in the 2.6 A crystal structure of intact rat P450R (Wang M et al., 1997, Proc Nat Acad Sci USA 94:8411-8416). The crystal structure of P450R-FMN reported here confirms the overall similarity of its alpha-beta-alpha architecture to that of the bacterial flavodoxins, but reveals differences in the position, number, and length of the helices relative to the central beta-sheet. The marked similarity between P450R-FMN and flavodoxins in the interactions between the FMN and the protein, indicate a striking evolutionary conservation of the FMN binding site. The P450R-FMN molecule has an unusual surface charge distribution, leading to a very strong dipole, which may be involved in docking cytochrome P450 into place for electron transfer near the FMN. Several acidic residues near the FMN are identified by mutagenesis experiments to be important for electron transfer to P4502D6 and to cytochrome c, a clear indication of the part of the molecular surface that is likely to be involved in substrate binding. Somewhat different parts are found to be involved in binding cytochrome P450 and cytochrome c.

Differences in a Conformational Equilibrium Distinguish Catalysis by the Endothelial and Neuronal Nitric-oxide Synthase Flavoproteins

“…Another question is whether the FMN redox state may impact the conformational equilibrium of an NOSr. In CPR, dissociation of the FMN subdomain from the FNR subdomain may depend on its reduction to FMNH 2 (61,62). Our current data are consistent with a similar behavior for eNOSr and nNOSr but also point out that dissociation of the FMN subdomain is not complete upon FMNH 2 formation, as evidenced by the sizeable fractions of fully reduced eNOSr and nNOSr that remain in the FMN-shielded conformation under the CaM-free condition.…”

Molecular view of an electron transfer process essential for iron–sulfur protein biogenesis

“…E-mail: banci@cerm.unifi.it. (FMN-Ndor1 hereafter) shows the classical fold of FMN-binding domains of diflavin reductases (20,21) and consists of a wound α-β-α fold with five parallel β-strands (the fifth strand divided in two short β-strands with a gap of four residues) in the core of the molecule flanked by two helices on one side (α1 and α5) and three (α2, α3, and α4) on the other (Fig. 1A and Table S1).…”

Human Cytochrome P450 Oxidoreductase Deficiency Caused by the Y181D Mutation: Molecular Consequences and Rescue of Defect

“…The structure of the full cytosolic catalytic domain of rat CYPOR (Wang et al, 1997), as well as that of the FMN binding domain of human CYPOR (Zhao et al, 1999), shows that in the WT enzyme, Y181 forms stacking interactions with the si-face of FMN (Fig. 1).…”