title: Endonuclease III is an iron-sulfur protein.
abstract: Elemental analyses, Mössbauer, and EPR data are reported to show that endonuclease III of Escherichia coli is an iron-sulfur protein. Mössbauer spectra of protein freshly prepared from E. coli grown on 57Fe-enriched medium demonstrate that the native enzyme contains a single 4Fe-4S cluster in the 2+ oxidation state, with a net spin of zero. Upon treatment with ferricyanide, a fraction (less than 25%) of the clusters is oxidized into a state which yields an EPR spectrum near g = 2.01 typical of a 3Fe-4S cluster. The magnetic field dependence of the linear electric field effect verifies this assignment. Electron spin echo modulation on the g = 2.01 form of the protein in deuterated solvent indicates the presence of exchangeable protons in the vicinity of the 3Fe-4S cluster. The data obtained show that the [4Fe-4S]2+ cluster of the native enzyme is resistant to either oxidation or reduction, although photoreduction elicited a g = 1.94 type EPR signal characteristic of a [4Fe-4S]1+ cluster. These studies show that endonuclease III is unique in being both a DNA repair enzyme and an iron-sulfur protein. The function of the 4Fe-4S cluster remains to be established.
authors.affiliation: Department of Biological Sciences, State University of New York, Albany 12222.
authors.forename: R P
authors.initials: RP
authors.lastname: Cunningham
authors.forename: H
authors.initials: H
authors.lastname: Asahara
authors.forename: J F
authors.initials: JF
authors.lastname: Bank
authors.forename: C P
authors.initials: CP
authors.lastname: Scholes
authors.forename: J C
authors.initials: JC
authors.lastname: Salerno
authors.forename: K
authors.initials: K
authors.lastname: Surerus
authors.forename: E
authors.initials: E
authors.lastname: Münck
authors.forename: J
authors.initials: J
authors.lastname: McCracken
authors.forename: J
authors.initials: J
authors.lastname: Peisach
authors.forename: M H
authors.initials: MH
authors.lastname: Emptage
mesh_terms: D043224:Deoxyribonuclease (Pyrimidine Dimer); D004578:Electron Spin Resonance Spectroscopy; D004706:Endodeoxyribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins / Q000378:metabolism*; D008667:Metalloproteins / Q000378:metabolism*; D015204:Spectroscopy, Mossbauer
chemical_list: D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins; D008667:Metalloproteins; D004706:Endodeoxyribonucleases; D043224:Deoxyribonuclease (Pyrimidine Dimer); C106403:NTH protein, E coli