NADPH Cytochrome P450 Oxidoreductase (or CYPOR) is a part of the P450 Cytochrome family that functions in transferring electrons from NADPH via cofactors FAD and FMN to other P450 cytochromes in the endoplasmic reticulum. CYPOR is a multimeric enzyme approximately 78kDa in size. CYPOR contains an N-terminal α-helix that anchors it in the endoplasmic reticulum membrane. The most C-terminal domain acts to bind NADH and FAD, and the N-terminal domain before the transmembrane anchor binds FMN. The FMN and FAD binding domains are separated by a connecting domain, which plays a role in allowing conformational change during electron transfer between the two flavin-containing domains. Crystal structures indicate the FMN domain is mobile with respect to the other domains.
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