title: Low temperature EPR and MCD studies on cytochrome b-558 of the Bacillus subtilis succinate: quinone oxidoreductase indicate bis-histidine coordination of the heme iron.
abstract: Bacillus subtilis cytochrome b-558 was expressed in high amounts in Escherichia coli, solubilized from membranes with detergent and purified free from other hemoproteins. The cytochrome possibly contains two heme groups. To determine the axial ligands to the low-spin heme and the heme rhombicity, the cytochrome was analyzed using low-temperature electron paramagnetic resonance (EPR) and magnetic circular dichroism (MCD) spectroscopy. The combined results exclude bis-methionine, bis-lysine and histidine-methionine coordination. Bis-histidine coordination of the heme(s) with a near perpendicular orientation of the imidazole planes is strongly suggested by the highly axial low-spin EPR signals and the intense near infrared MCD spectrum (delta epsilon = 380 M-1.cm-1 at 4.2 K and 5 T) of the charge-transfer band at 1600 nm.
authors.affiliation: Department of Microbiology, University of Lund, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Fridén
authors.forename: M R
authors.initials: MR
authors.lastname: Cheesman
authors.forename: L
authors.initials: L
authors.lastname: Hederstedt
authors.forename: K K
authors.initials: KK
authors.lastname: Andersson
authors.forename: A J
authors.initials: AJ
authors.lastname: Thomson
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002942:Circular Dichroism; D003001:Cloning, Molecular; D003573:Cytochrome b Group / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D042963:Electron Transport Complex II; D004926:Escherichia coli / Q000235:genetics; D005615:Freezing; D006418:Heme / Q000378:metabolism*; D006639:Histidine; D007501:Iron / Q000378:metabolism; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D019255:NADPH Oxidases; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D013385:Succinate Dehydrogenase / Q000235:genetics / Q000378:metabolism*
chemical_list: D003573:Cytochrome b Group; D009097:Multienzyme Complexes; D006418:Heme; D006639:Histidine; C036888:cytochrome b558; D007501:Iron; D010088:Oxidoreductases; D042963:Electron Transport Complex II; D013385:Succinate Dehydrogenase; D019255:NADPH Oxidases