Kappler, Ulrike and Bennett, Brian and Rethmeier, Jörg and Schwarz, Guenther and Deutzmann, Rainer and McEwan, Alistair G. and Dahl, Christiane (2000) Sulfite : Cytochrome c oxidoreductase from Thiobacillus novellus - Purification, characterization, and molecular biology of a heterodimeric member of the sulfite oxidase family. JOURNAL OF BIOLOGICAL CHEMISTRY, 275 (18). pp. 13202-13212. ISSN 0021-9258
Full text not available from this repository. (Request a copy)Abstract
Direct oxidation of sulfite to sulfate occurs in various photo- and chemotrophic sulfur oxidizing microorganisms as the final step in the oxidation of reduced sulfur compounds and is catalyzed by sulfite:cytochrome c oxidoreductase (EC 1.8.2.1), Here we show that the enzyme from Thiobacillus novellus is a periplasmically located alpha beta heterodimer, consisting of a 40.6-kDa subunit containing a molybdenum cofactor and an 8.8-kDa monoheme cytochrome c(552) smbunit (midpoint redox potential, Em(8.0) = +280 mV), The organic component of the molybdenum cofactor was identified as molybdopterin contained in a 1:1 ratio to the Mo content of the enzyme. Electron paramagnetic resonance spectroscopy revealed the presence of a sulfite-inducible Mo(V) signal characteristic of sulfite:acceptor oxidoreductases. However, pH-dependent changes in the electron paramagnetic resonance signal were not detected. Kinetic studies showed that the enzyme exhibits a ping-pong mechanism involving two reactive sites. K-m values for sulfite and cytochrome c(550) were determined to be 27 and 4 mu M, respectively; the enzyme was found to be reversibly inhibited by sulfate and various buffer ions. The sorAB genes, which encode the enzyme, appear to form an operon, which is preceded by a putative extracytoplasmic function-type promoter and contains a hairpin loop termination structure downstream of sorB. While SorA exhibits significant similarities to known sequences of eukaryotic and bacterial sulfite:acceptor oxidoreductases, SorB does not appear to be closely related to any known c-type cytochromes.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | PERIPLASMIC NITRATE REDUCTASE; PARACOCCUS-DENITRIFICANS; CHICKEN LIVER; XANTHINE DEHYDROGENASE; RHODOBACTER-CAPSULATUS; MOLYBDENUM COFACTOR; SULFUR OXIDATION; ESCHERICHIA-COLI; BACTERIA; PROTEINS; |
| Subjects: | 500 Science > 570 Life sciences |
| Divisions: | Biology, Preclinical Medicine > Institut für Biochemie, Genetik und Mikrobiologie > Lehrstuhl für Biochemie I > Prof. Dr. Rainer Deutzmann |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 03 May 2022 13:24 |
| Last Modified: | 03 May 2022 13:24 |
| URI: | https://pred.uni-regensburg.de/id/eprint/42488 |
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