| The functionality of the interaction was demonstrated by investigating the inhibition of neuronal nitric oxide synthase 1 ( NOS 1 ) ; PMCA is a negative regulator of NOS 1 dependent NO production , and overexpression of alpha 1 syntrophin and PMCA 4 resulted in strongly increased inhibition of NO production . ^^^ These results suggest that PMCA 4 is tethered to the syntrophin complex as a regulator of NOS 1 , but its absence does not cause collapse of the complex , contrary to what has been reported for other proteins within the complex , such as dystrophin . ^^^ |