title: Sulfolobus acidocaldarius terminal oxidase. A kinetic investigation and its structural interpretation.
abstract: The thermoacidophilic archaebacterium Sulfolobus acidocaldarius possesses a very unusual terminal oxidase. We report original kinetic experiments on membranes of this microorganism carried out by stopped flow, using time-resolved optical spectroscopy combined with singular value decomposition analysis. The reduced-oxidized kinetic difference spectrum of the Sulfolobus membranes is characterized by three significant peaks in the visible region at 605, 586, and 560 nm. The 605-nm peak and part of the 586-nm peak (cytochrome aa3-type quinol oxidase) are reduced synchronously by both ascorbate plus N,N,N',N'-tetramethyl-p-phenylendiamine (TMPD) and dithionite, and they are very rapidly oxidized by molecular oxygen. A second pool of cytochromes seems to contribute to the 586-nm peak which is not reduced by ascorbate plus TMPD and reacts very slowly with dithionite. The b-type cytochromes (560 nm peak) are reduced by both reductants and are essentially "non-autoxidizable" at room temperature. Only one CO binding site with spectral features, kinetic properties, and ligand affinity not very dissimilar from those of mammalian cytochrome oxidase can be detected in the ascorbate-reduced membranes. On the contrary, a second CO binding site having unusual properties for aa3 terminal oxidases can be detected in the dithionite-reduced membranes.
authors.affiliation: Department of Biochemical Sciences, University of Rome, La Sapienza, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Giuffrè
authors.forename: G
authors.initials: G
authors.lastname: Antonini
authors.forename: M
authors.initials: M
authors.lastname: Brunori
authors.forename: E
authors.initials: E
authors.lastname: D'Itri
authors.forename: F
authors.initials: F
authors.lastname: Malatesta
authors.forename: F
authors.initials: F
authors.lastname: Nicoletti
authors.forename: S
authors.initials: S
authors.lastname: Anemüller
authors.forename: M
authors.initials: M
authors.lastname: Gleissner
authors.forename: G
authors.initials: G
authors.lastname: Schäfer
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry; D002248:Carbon Monoxide / Q000378:metabolism; D004227:Dithionite / Q000737:chemistry; D007700:Kinetics; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism; D010100:Oxygen / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D016945:Sulfolobus acidocaldarius / Q000201:enzymology*; D013772:Tetramethylphenylenediamine / Q000737:chemistry
chemical_list: D004227:Dithionite; D002248:Carbon Monoxide; D010088:Oxidoreductases; D013772:Tetramethylphenylenediamine; D001205:Ascorbic Acid; D010100:Oxygen