title: Heme-assisted S-nitrosation desensitizes ferric soluble guanylate cyclase to nitric oxide.
abstract: Nitric oxide (NO) signaling regulates key processes in cardiovascular physiology, specifically vasodilation, platelet aggregation, and leukocyte rolling. Soluble guanylate cyclase (sGC), the mammalian NO sensor, transduces an NO signal into the classical second messenger cyclic GMP (cGMP). NO binds to the ferrous (Fe(2+)) oxidation state of the sGC heme cofactor and stimulates formation of cGMP several hundred-fold. Oxidation of the sGC heme to the ferric (Fe(3+)) state desensitizes the enzyme to NO. The heme-oxidized state of sGC has emerged as a potential therapeutic target in the treatment of cardiovascular disease. Here, we investigate the molecular mechanism of NO desensitization and find that sGC undergoes a reductive nitrosylation reaction that is coupled to the S-nitrosation of sGC cysteines. We further characterize the kinetics of NO desensitization and find that heme-assisted nitrosothiol formation of β1Cys-78 and β1Cys-122 causes the NO desensitization of ferric sGC. Finally, we provide evidence that the mechanism of reductive nitrosylation is gated by a conformational change of the protein. These results yield insights into the function and dysfunction of sGC in cardiovascular disease.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA.
authors.forename: Nathaniel B
authors.initials: NB
authors.lastname: Fernhoff
authors.forename: Emily R
authors.initials: ER
authors.lastname: Derbyshire
authors.forename: Eric S
authors.initials: ES
authors.lastname: Underbakke
authors.forename: Michael A
authors.initials: MA
authors.lastname: Marletta
mesh_terms: D000478:Alkylation; D000818:Animals; D020134:Catalytic Domain; D003545:Cysteine / Q000378:metabolism; D006162:Guanylate Cyclase / Q000737:chemistry / Q000378:metabolism*; D006418:Heme / Q000378:metabolism*; D006801:Humans; D006878:Hydroxides / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D007700:Kinetics; D050505:Mutant Proteins / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D015538:Nitrosation; D009711:Nucleotides / Q000378:metabolism; D010084:Oxidation-Reduction; D011485:Protein Binding; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000378:metabolism*; D000071756:Soluble Guanylyl Cyclase; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D006878:Hydroxides; D050505:Mutant Proteins; D009711:Nucleotides; D018160:Receptors, Cytoplasmic and Nuclear; D013438:Sulfhydryl Compounds; D009569:Nitric Oxide; D006418:Heme; C031356:hydroxide ion; D007501:Iron; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D003545:Cysteine