title: On the oxygen reactivity of flavoprotein oxidases: an oxygen access tunnel and gate in brevibacterium sterolicum cholesterol oxidase.
abstract: The flavoprotein cholesterol oxidase from Brevibacterium sterolicum (BCO) possesses a narrow channel that links the active center containing the flavin to the outside solvent. This channel has been proposed to serve for the access of dioxygen; it contains at its "bottom" a Glu-Arg pair (Glu-475-Arg-477) that was found by crystallographic studies to exist in two forms named "open" and "closed," which in turn was suggested to constitute a gate functioning in the control of oxygen access. Most mutations of residues that flank the channel have minor effects on the oxygen reactivity. Mutations of Glu-311, however, cause a switch in the basic kinetic mechanism of the reaction of reduced BCO with dioxygen; wild-type BCO and most mutants show a saturation behavior with increasing oxygen concentration, whereas for Glu-311 mutants a linear dependence is found that is assumed to reflect a "simple" second order process. This is taken as support for the assumption that residue Glu-311 finely tunes the Glu-475-Arg-477 pair, forming a gate that functions in modulating the access/reactivity of dioxygen.
authors.affiliation: Department of Biotechnology and Molecular Sciences, University of Insubria, 21100 Varese, Italy.
authors.forename: Luciano
authors.initials: L
authors.lastname: Piubelli
authors.forename: Mattia
authors.initials: M
authors.lastname: Pedotti
authors.forename: Gianluca
authors.initials: G
authors.lastname: Molla
authors.forename: Susanne
authors.initials: S
authors.lastname: Feindler-Boeckh
authors.forename: Sandro
authors.initials: S
authors.lastname: Ghisla
authors.forename: Mirella S
authors.initials: MS
authors.lastname: Pilone
authors.forename: Loredano
authors.initials: L
authors.lastname: Pollegioni
mesh_terms: D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D001665:Binding Sites / Q000235:genetics; D001951:Brevibacterium / Q000201:enzymology* / Q000235:genetics; D002789:Cholesterol Oxidase / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray; D005420:Flavoproteins / Q000737:chemistry* / Q000235:genetics; D007700:Kinetics; D020125:Mutation, Missense; D010100:Oxygen / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D005420:Flavoproteins; D002789:Cholesterol Oxidase; D010100:Oxygen