The novel binding mode of N-alkyl-N'-hydroxyguanidine to neuronal nitric oxide synthase provides mechanistic insights into NO biosynthesis.
A series of N-alkyl-N'-hydroxyguanidine compounds have recently been characterized as non-amino acid substrates for all three nitric oxide synthase (NOS) isoforms which mimic NO formation from N(omega)-hydroxy-L-arginine. Crystal structures of the nNOS heme domain complexed with either N-isopropyl-N'-hydroxyguanidine or N-butyl-N'-hydroxyguanidine reveal two different binding modes in the substrate binding pocket. The binding mode of the latter is consistent with that observed for the substrate N(omega)-hydroxy-L-arginine bound in the nNOS active site. However, the former binds to nNOS in an unexpected fashion, thus providing new insights into the mechanism on how the hydroxyguanidine moiety leads to NO formation. Structural features of substrate binding support the view that the OH-substituted guanidine nitrogen, instead of the hydroxyl oxygen, is the source of hydrogen supplied to the active ferric-superoxy species for the second step of the NOS catalytic reaction.
Li
Huiying
H
Department of Molecular Biology and Biochemistry and Program in Macromolecular Structures, University of California, Irvine, California 92697, USA.
Shimizu
Hideaki
H
Flinspach
Mack
M
Jamal
Joumana
J
Yang
Weiping
W
Xian
Ming
M
Cai
Tingwei
T
Wen
Edward Zhong
EZ
Jia
Qiang
Q
Wang
Peng George
PG
Poulos
Thomas L
TL
D000478:Alkylation; D000818:Animals; D001665:Binding Sites; D003001:Cloning, Molecular; D006146:Guanidines / Q000737:chemistry* / Q000493:pharmacokinetics; D006898:Hydroxylamines; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000737:chemistry* / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I; D011487:Protein Conformation; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
D006146:Guanidines; D006898:Hydroxylamines; D007527:Isoenzymes; D011994:Recombinant Proteins; D009569:Nitric Oxide; C029604:hydroxyguanidine; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat