On the oxygen reactivity of flavoprotein oxidases: an oxygen access tunnel and gate in brevibacterium sterolicum cholesterol oxidase.
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.
Piubelli
Luciano
L
Department of Biotechnology and Molecular Sciences, University of Insubria, 21100 Varese, Italy.
Pedotti
Mattia
M
Molla
Gianluca
G
Feindler-Boeckh
Susanne
S
Ghisla
Sandro
S
Pilone
Mirella S
MS
Pollegioni
Loredano
L
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
D001426:Bacterial Proteins; D005420:Flavoproteins; D002789:Cholesterol Oxidase; D010100:Oxygen