Intense interest in the action and synthesis of nitric oxide has fuelled st
ructural studies of nitric oxide synthase (NOS). The monomeric and dimeric
heme domains of inducible NOS were the first NOS structures to be described
. A recent independent analysis of the corresponding heme domains from endo
thelial NOS confirms most of the features found earlier and also reveals a
novel Zn(Cys)(4) center - a new feature far NOS.