title: The cysteine residue of the SoxY protein as the active site of protein-bound sulfur oxidation of Paracoccus pantotrophus GB17.
abstract: Four proteins of Paracoccus pantotrophus are required for hydrogen sulfide-, sulfur-, thiosulfate- and sulfite-dependent horse heart cytochrome c reduction. The lack of free intermediates suggested a protein-bound sulfur oxidation mechanism. The SoxY protein has a novel motif containing a cysteine residue. Electrospray ionization and matrix-assisted laser desorption ionization mass spectrometry of the SoxYZ protein revealed one mass for SoxZ and different masses for SoxY, indicating native SoxY (10977 Da) and SoxY with additional masses of +32, +80, +112 and +144 Da, suggesting addition of sulfur, sulfite, thiosulfate and thioperoxomonosulfate. Reduction of SoxY removed the additional masses, indicating a thioether or thioester bond. N-Ethylmaleimide inhibited thiosulfate-oxidation and the kinetics suggested a turn-over-dependent mode of action. These data were evidence that the sulfur atom to be oxidized was covalently linked to the thiol moiety of the cysteine residue of SoxY and the active site of sulfur oxidation.
authors.affiliation: Lehrstuhl für Technische Mikrobiologie, Fachbereich Chemietechnik, Universität Dortmund, Emil-Figge-Strasse 66, D-44221 Dortmund, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Quentmeier
authors.forename: C G
authors.initials: CG
authors.lastname: Friedrich
mesh_terms: D001426:Bacterial Proteins; D020134:Catalytic Domain; D003545:Cysteine / Q000737:chemistry; D005033:Ethylmaleimide; D007700:Kinetics; D008970:Molecular Weight; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D010230:Paracoccus / Q000201:enzymology*; D011485:Protein Binding; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013455:Sulfur / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D013438:Sulfhydryl Compounds; D013455:Sulfur; D010088:Oxidoreductases; D003545:Cysteine; D005033:Ethylmaleimide