TY - JOUR
T1 - Characterization by electron paramagnetic resonance of the interactions of L-arginine and L-thiocitrulline with the heme cofactor region of nitric oxide synthase
AU - Salerno, J. C.
AU - Frey, C.
AU - McMillan, K.
AU - Williams Masters, R. F.B.S.S.
AU - Griffith, O. W.
N1 - Copyright:
Copyright 2004 Elsevier B.V., All rights reserved.
PY - 1995
Y1 - 1995
N2 - Nitric oxide synthase (NOS) catalyzes sequential NADPH- and O2-dependent mono-oxygenase reactions converting L-arginine to N(ω)-hydroxy-L-arginine and N(ω) hydroxy-L-arginine to citrulline and nitric oxide. The homodimeric enzyme contains one heme/monomer, and that cofactor is thought to mediate both partial reactions. Here we show by electron paramagnetic resonance spectroscopy that binding of substrate L-arginine to neuronal NOS perturbs the heme cofactor binding pocket without directly interacting as a sixth axial heine ligand; heme iron is exclusively high spin. In contrast, binding of L-thiocitrulline, a NOS inhibitor, produces both high and low spin iron spectra; L-thiocitrulline sulfur is a sixth axial heine ligand in one, but not all, of the low spin forms. The high spin forms of the L-thiocitrulline NOS complex display a distortion in the opposite direction to that caused by L-arginine binding. The findings elucidate the binding interactions of L- arginine and L-thiocitrulline to neuronal NOS and demonstrate that each causes a unique perturbation to the heine cofactor pocket of NOS.
AB - Nitric oxide synthase (NOS) catalyzes sequential NADPH- and O2-dependent mono-oxygenase reactions converting L-arginine to N(ω)-hydroxy-L-arginine and N(ω) hydroxy-L-arginine to citrulline and nitric oxide. The homodimeric enzyme contains one heme/monomer, and that cofactor is thought to mediate both partial reactions. Here we show by electron paramagnetic resonance spectroscopy that binding of substrate L-arginine to neuronal NOS perturbs the heme cofactor binding pocket without directly interacting as a sixth axial heine ligand; heme iron is exclusively high spin. In contrast, binding of L-thiocitrulline, a NOS inhibitor, produces both high and low spin iron spectra; L-thiocitrulline sulfur is a sixth axial heine ligand in one, but not all, of the low spin forms. The high spin forms of the L-thiocitrulline NOS complex display a distortion in the opposite direction to that caused by L-arginine binding. The findings elucidate the binding interactions of L- arginine and L-thiocitrulline to neuronal NOS and demonstrate that each causes a unique perturbation to the heine cofactor pocket of NOS.
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U2 - 10.1074/jbc.270.46.27423
DO - 10.1074/jbc.270.46.27423
M3 - Article
C2 - 7499198
AN - SCOPUS:0028802346
VL - 270
SP - 27423
EP - 27428
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 46
ER -