FIG. 2. Molecular isoforms of NOS. Diagrammatic representation of the structure of cloned isoforms of NOS and cytochrome P-450 reductase. P, consensus sequence for phosphorylation by cAMP-dependent protein kinase; CAL, calmodulin binding site; FMN, flavin mononucleotide; FAD, flavin adenine dinucleotide; NADPH, reduced form of nicotinamide adenine dinucleotide phosphate; TMD, transmembrane domain.