ArticleCovalent structure of the flavoprotein subunit of the flavocytochrome c: Sulfide dehydrogenase from the purple phototrophic bacterium chromatium vinosum |
| Gonzalez Van Driessche 1, Monjoo Koh 1 a, Jozef J. Van Beeumen 1 *, Zhi-Wei Chen 2, F. Scott Mathews 2, Terry E. Meyer 3, Robert G. Bartsch 3, Michael A. Cusanovich 3 |
1Department of Biochemistry, Physiology and Microbiology, Laboratory of Protein Biochemistry and Protein Engineering, State University of Gent, B-9000 Gent, Belgium
2Department of Biochemistry, Washington University School of Medicine, St. Louis, Missouri 63110
3Department of Biochemistry, University of Arizona, Tucson, Arizona 85721
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| email: Jozef J. Van Beeumen (vbeeumenlmgmicro) |
*Correspondence to Jozef J. Van Beeumen, Vakgroep Biochemie, Fysiologie en Microbiologic Universiteit Gent, Ledeganckstraat 35, B-9000 Gent, Belgium
aCurrent address: Department of Chemistry, Chosun University, Kwangju, Seoul 501-759, Korea
Funded by:
National Institutes of Health; Grant Number: GM21277, GM21514
Concerted Research Action of the Flemish Government; Grant Number: 120.52293
Belgian National Fund for Joint Basic Research; Grant Number: 32001891
| amino acid sequence glutathione reductase protein mass spectrometry |
| The amino acid sequence of the flavoprotein subunit of Chromatium vinosum flavocytochrome c - sulftde dehydrogenase (FCSD) was determined by automated Edman degradation and mass spectrometry in conjunction with the three-dimensional structure determination (Chen Z et al., 1994, Science 266:430-432). The sequence of the diheme cytochrome c subunit was determined previously. The flavoprotein contains 401 residues and has a calculated protein mass, including FAD, of 43,568 Da, compared with a mass of 43,652 ± 44 Da measured by LDMS. There are six cysteine residues, among which Cys 42 provides the site of covalent attachment of the FAD. Cys 161 and Cys 337 form a disulfide bond adjacent to the FAD. The flavoprotein subunit of FCSD is most closely related to glutathione reductase (GR) in three-dimensional structure and, like that protein, contains three domains. However, approximately 20 insertions and deletions are necessary for alignment and the overall identity in sequence is not significantly greater than for random comparisons. The first domain binds FAD in both proteins. Domain 2 of GR is the site of NADP binding, but has an unknown role in FCSD. We postulate that it is the binding site for a cofactor involved in oxidation of reduced sulfur compounds. Domains 1 and 2 of FCSD, as of GR, are homologous to one another and represent an ancient gene doubling. The third domain provides the dimerization interface for GR, but is the site of binding of the cytochrome subunit in FCSD. The four functional entities, predicted to be near the FAD from earlier studies of the kinetics of sulfite adduct formation and decay, have now been identified from the three-dimensional structure and the sequence as Cys 161/Cys 337 disulfide, Tip 391, Glu 167, and the positive end of a helix dipole. |
Received: 20 March 1996; Accepted: 14 April 1996
10.1002/pro.5560050901
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