The @entity842 synthases (NOSs) are comprised of an oxygenase domain and a reductase domain bisected by a calmodulin (CaM) binding region. The NOS reductase domains share approximately 60% sequence similarity with the @entity13324 ( @entity13324 ), which transfers electrons to microsomal cytochromes P450. The crystal structure of the @entity2821 ( @entity2821 ) connecting/FAD binding subdomains reveals that the structure of the @entity2821 -connecting subdomain diverges from that of @entity13324 , implying different alignments of the @entity28094 in the two enzymes. We created a series of chimeric enzymes between @entity2821 and @entity13324 in which the @entity21890 binding and the connecting/FAD binding subdomains are swapped. A chimera consisting of the @entity2821 heme domain and @entity21890 binding subdomain and the @entity13324 FAD binding subdomain catalyzed significantly increased rates of @entity4674 reduction in the absence of CaM and of NO synthesis in its presence. @entity4674 reduction by this chimera was inhibited by CaM. Other chimeras consisting of the @entity2821 heme domain, the @entity13324 @entity21890 binding subdomain, and the @entity2821 FAD binding subdomain with or without the tail region also catalyzed @entity4674 reduction, were not modulated by CaM, and could not transfer electrons into the heme domain. A chimera consisting of the heme domain of @entity2821 and the reductase domain of @entity13324 reduced @entity4674 and @entity9588 at rates 2-fold higher than that of native @entity13324 , suggesting that the presence of the @entity1446 domain affected electron transfer through the reductase domain. These data demonstrate that the @entity21890 subdomain of @entity13324 cannot effectively substitute for that of @entity2821 , whereas the FAD subdomains are interchangeable. The differences among these chimeras most likely result from alterations in the alignment of the @entity28094 within each enzyme construct.

Chimeric enzymes of @entity13324 and neuronal XXXX synthase reductase domain reveal structural and functional differences.

@entity4674 :: ('54205', 'Gene') :: ['Cytochrome c', 'cytochrome c'] @entity21890 :: ('342184', 'Gene') :: ['FMN'] @entity2821 :: ('4842', 'Gene') :: ['nNOS', 'neuronal NOS'] @entity28094 :: ('MESH:D005415', 'Chemical') :: ['flavins'] @entity842 :: ('MESH:D009569', 'Chemical') :: ['nitric-oxide'] @entity9588 :: ('MESH:C007931', 'Chemical') :: ['ferricyanide'] @entity13324 :: ('5447', 'Gene') :: ['CYPOR', 'cytochrome P450 oxidoreductase'] @entity1446 :: ('MESH:D006418', 'Chemical') :: ['heme']
@entity842 :: (MESH:D009569,Chemical) :: ['nitric-oxide']
