title: Unusual cyanide bindings to a heme-regulated phosphodiesterase from Escherichia coli: effect of Met95 mutations.
abstract: In order to understand heme environment of a heme-regulated phosphodiesterase (Ec DOS), the binding behavior of cyanide to the Fe (III) complex was examined. Interestingly, the rate of cyanide binding to full-length Ec DOS was unusually slow with k(on)=0.0022mM(-1)s(-1), while the rate for the isolated heme domain of Ec DOS (0.045mM(-1)s(-1)) was 20-fold higher. Ala and Leu mutations at Met95, which has been suggested to be a heme axial ligand, increased the k(on) rate 11- and 8-fold, respectively, and dramatically decreased the cyanide dissociation rate from the isolated heme domain. His mutation at Met95, on the other hand, caused a 17-fold decrease in the k(on) value. We discuss the unusual cyanide binding behavior and the role of Met95 in controlling cyanide binding.
authors.affiliation: Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, 980-8577, Sendai, Japan.
authors.forename: Miki
authors.initials: M
authors.lastname: Watanabe
authors.forename: Toshitaka
authors.initials: T
authors.lastname: Matsui
authors.forename: Yukie
authors.initials: Y
authors.lastname: Sasakura
authors.forename: Ikuko
authors.initials: I
authors.lastname: Sagami
authors.forename: Toru
authors.initials: T
authors.lastname: Shimizu
mesh_terms: D001386:Azides / Q000378:metabolism; D003486:Cyanides / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D005459:Fluorides / Q000378:metabolism; D006418:Heme / Q000378:metabolism*; D007093:Imidazoles / Q000378:metabolism; D007501:Iron / Q000378:metabolism; D007700:Kinetics; D008715:Methionine / Q000235:genetics*; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010727:Phosphoric Diester Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013053:Spectrophotometry
chemical_list: D001386:Azides; D003486:Cyanides; D007093:Imidazoles; D006418:Heme; D008715:Methionine; D007501:Iron; D010727:Phosphoric Diester Hydrolases; D005459:Fluorides