title: Action of hexaamminecobalt on the activity of Serratia marcescens nuclease.
abstract: Using CD spectroscopic and kinetic analysis, a refined mechanism of Co(NH3)6(3+) action on activity of Serratia marcescens nuclease was elucidated. The mechanism was identical with previously found mechanisms of Mg2+ and C7H5O2Hg+. Similarly to Mg2+ and C7H5O2Hg+, Co(NH3)6(3+) binding to the DNA substrate induced changes in the secondary structure which resulted in changes of the enzymatic activity of the S. marcescens nuclease. Upon binding of 0.03 Co(NH3)6(3+) per DNA phosphate, highly polymerized DNA displayed A-form characteristics. The DNA transition from B-form to A-form intermediate was followed by a decrease of the nuclease activity. The diminishing nuclease activity was consistent with diminishing values of Km and Kcat. Co(NH3)6(3+) binding to the highly polymerized DNA caused a 1.7-2.8-fold decrease in Km, and 13.3-19.9 decrease in Vmax compared with Mg-DNA complex. A vast excess of Co(NH3)6(3+) did not affect the activity of S. marcescens nuclease if the DNA in the assay mixture remained in its B-form conformation. Preincubation of S. marcescens nuclease with Co(NH3)6(3+) did not influence the tertiary structure of the enzyme.
authors.affiliation: Department of Microbiology, Kazan State University, Kremliovskaya st. 18, Kazan, 420008 Russia. Maria.Filimonova@ksu.ru
authors.forename: Maria
authors.initials: M
authors.lastname: Filimonova
authors.forename: Valentina
authors.initials: V
authors.lastname: Gubskaya
authors.forename: Il'dus
authors.initials: I
authors.lastname: Nuretdinov
authors.forename: Inna
authors.initials: I
authors.lastname: Leshchinskaya
mesh_terms: D001667:Binding, Competitive; D002412:Cations / Q000494:pharmacology; D002942:Circular Dichroism / Q000379:methods; D003035:Cobalt / Q000378:metabolism / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004722:Endoribonucleases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007700:Kinetics; D008278:Magnesium Sulfate / Q000494:pharmacology; D009690:Nucleic Acid Conformation / Q000187:drug effects; D012706:Serratia marcescens / Q000187:drug effects / Q000201:enzymology / Q000235:genetics
chemical_list: D002412:Cations; D004269:DNA, Bacterial; C030862:cobalt ammonium complex; D003035:Cobalt; D008278:Magnesium Sulfate; D004706:Endodeoxyribonucleases; D004722:Endoribonucleases; C021835:Serratia marcescens nuclease