title: YC-1 facilitates release of the proximal His residue in the NO and CO complexes of soluble guanylate cyclase.
abstract: The benzylindazole compound YC-1 has been shown to activate soluble guanylate cyclase by increasing the sensitivity toward NO and CO. Here we report the action of YC-1 on the coordination of CO- and NO-hemes in the enzyme and correlate the events with the activation of enzyme catalysis. A single YC-1-binding site on the heterodimeric enzyme was identified by equilibrium dialysis. To explore the affect of YC-1 on the NO-heme coordination, the six-coordinate NO complex of the enzyme was stabilized by dibromodeuteroheme substitution. Using the dibromodeuteroheme enzyme, YC-1 converted the six-coordinate NO-heme to a five-coordinate NO-heme with a characteristic EPR signal that differed from that in the absence of YC-1. These results revealed that YC-1 facilitated cleavage of the proximal His-iron bond and caused geometrical distortion of the five-coordinate NO-heme. Resonance Raman studies demonstrated the presence of two iron-CO stretch modes at 488 and 521 cm(-1) specific to the YC-1-bound CO complex of the native enzyme. Together with the infrared C-O stretching measurements, we assigned the 488-cm(-1) band to the iron-CO stretch of a six-coordinate CO-heme and the 521-cm(-1) band to the iron-CO stretch of a five-coordinate CO-heme. These results indicate that YC-1 stimulates enzyme activity by weakening or cleaving the proximal His-iron bond in the CO complex as well as the NO complex.
authors.affiliation: Department of Life Science, College of Science, Rikkyo University, Nishi-ikebukuro 3-34-1, Toshima-ku, Tokyo 171-8501, Japan. rmakino@rikkyo.ne.jp
authors.forename: Ryu
authors.initials: R
authors.lastname: Makino
authors.forename: Eiji
authors.initials: E
authors.lastname: Obayashi
authors.forename: Nana
authors.initials: N
authors.lastname: Homma
authors.forename: Yoshitsugu
authors.initials: Y
authors.lastname: Shiro
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hori
mesh_terms: D000818:Animals; D002248:Carbon Monoxide / Q000378:metabolism*; D002417:Cattle; D004578:Electron Spin Resonance Spectroscopy; D006162:Guanylate Cyclase / Q000737:chemistry / Q000378:metabolism*; D006639:Histidine / Q000378:metabolism*; D007191:Indazoles / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism*
chemical_list: D007191:Indazoles; C090937:3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole; D009569:Nitric Oxide; D006639:Histidine; D002248:Carbon Monoxide; D006162:Guanylate Cyclase