During catalysis the flavoprotein domain of neuronal nitric-oxide synthase (nNOS) shuttles NADPH-derived reducing equivalents from FAD to FMN and then to the P450-heme enabling heme-based oxygen activation and subsequent NO-synthesis. The binding of Ca²⁺-activated calmodulin (Ca²⁺-CaM) to nNOS alleviates inhibition of flavin mediated electron transfer within the diflavin domain, which...