title: An enzyme-linked receptor mechanism for nitric oxide-activated guanylyl cyclase.
abstract: Nitric oxide (NO) exerts physiological effects by activating specialized receptors that are coupled to guanylyl cyclase activity, resulting in cGMP synthesis from GTP. Despite its widespread importance as a signal transduction pathway, the way it operates is still understood only in descriptive terms. The present work aimed to elucidate a formal mechanism for NO receptor activation and its modulation by GTP, ATP, and allosteric agents, such as YC-1 and BAY 41-2272. The model comprised a module in which NO, the nucleotides, and allosteric agents bind and the protein undergoes a conformational change, dovetailing with a catalytic module where GTP is converted to cGMP and pyrophosphate. Experiments on NO-activated guanylyl cyclase purified from bovine lung allowed values for all of the binding and isomerization constants to be derived. The catalytic module was a modified version of one describing the kinetics of adenylyl cyclase. The resulting enzyme-linked receptor mechanism faithfully reproduces all of the main functional properties of NO-activated guanylyl cyclase reported to date and provides a thermodynamically sound interpretation of those properties. With appropriate modification, it also replicates activation by carbon monoxide and the remarkable enhancement of that activity brought about by the allosteric agents. In addition, the mechanism enhances understanding of the behavior of the receptor in a cellular setting.
authors.affiliation: Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: Brijesh
authors.initials: B
authors.lastname: Roy
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Halvey
authors.forename: John
authors.initials: J
authors.lastname: Garthwaite
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000737:chemistry / Q000378:metabolism; D000494:Allosteric Regulation / Q000502:physiology; D000818:Animals; D002417:Cattle; D006152:Cyclic GMP / Q000737:chemistry / Q000378:metabolism; D004789:Enzyme Activation / Q000502:physiology; D006160:Guanosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D006162:Guanylate Cyclase / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D007191:Indazoles / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008168:Lung / Q000201:enzymology*; D008956:Models, Chemical; D009569:Nitric Oxide / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000502:physiology; D011720:Pyrazoles; D011725:Pyridines; D011755:Pyrophosphatases / Q000737:chemistry / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry* / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D000071756:Soluble Guanylyl Cyclase; D013816:Thermodynamics
chemical_list: C423582:3-(4-Amino-5-cyclopropylpyrimidine-2-yl)-1-(2-fluorobenzyl)-1H-pyrazolo(3,4-b)pyridine; D007191:Indazoles; D011720:Pyrazoles; D011725:Pyridines; D018160:Receptors, Cytoplasmic and Nuclear; C090937:3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole; D009569:Nitric Oxide; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D011755:Pyrophosphatases; D000262:Adenylyl Cyclases; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D006152:Cyclic GMP