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EPR Studies of the Mitochondrial Alternative Oxidase: EVIDENCE FOR A DIIRON CARBOXYLATE CENTER
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
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2002 In: Journal of Biological Chemistry, ISSN 0021-9258, Vol. 277, no 46, 43608-43614 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2002. Vol. 277, no 46, 43608-43614 p.
URN: urn:nbn:se:su:diva-23743OAI: diva2:194318
Part of urn:nbn:se:su:diva-472Available from: 2005-04-21 Created: 2005-04-21Bibliographically approved
In thesis
1. Structural and Functional Studies of Diiron Carboxylate Proteins
Open this publication in new window or tab >>Structural and Functional Studies of Diiron Carboxylate Proteins
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Iron is essential to all life; it is a vital component of many proteins in humans as well as plants and bacteria. Because of the ability of iron to activate oxygen, it is often found in proteins that interact with oxygen in some way. One of the protein families that utilize iron to harness the oxidative power of the oxygen molecule for different purposes is the diiron carboxylate protein family. These proteins have two iron ions bound in the active site that are coordinated by four carboxylic residues and two histidines. These enzymes catalyse reactions such as radical generation, ubiquinol oxidation, fatty acid desaturation, iron oxidation and many different hydroxylation reactions. One subgroup of this protein family that recently has been discovered contains the membrane-bound diiron carboxylate proteins. In this thesis we have studied three diiron carboxylate proteins. The first, alternative oxidase, is a membrane-bound ubiquinol oxidase present in the respiratory chain of plants, some yeasts and protozoa. We have obtained the first spectroscopical evidence for the presence of a diiron carboxylate site in alternative oxidase. We have also identified the first prokaryotic alternative oxidase and shown it to be expressed and functional. The second membrane-bound diiron carboxylate protein studied is Coq7; the inactivation of this protein has been reported to prolong the life span of the model organism Caenorhabditis elegans. We have shown that Coq7 catalyses a hydroxylation in the biosynthesis of ubiquinone and identified it as a diiron carboxylate protein. Finally we have solved the structure of the ribonucleotide reductase R2 subunit from Chlamydia trachomatis, a soluble diiron carboxylate protein. We have discovered that this is an unusual member of the R2 family because it challenges the generally accepted dogma of a conserved radical-harbouring tyrosine being a requirement for enzyme activity in this protein class. We have by EPR spectroscopy demonstrated that the radical in this protein is stored as a high-valent species at the diiron site instead of on a tyrosine. We also found that many organisms, including several human pathogens, have R2 proteins with the same sequence abnormalities and propose that these proteins constitute a new ribonucleotide reductase subclass, class Ic.

Place, publisher, year, edition, pages
Stockholm: Institutionen för biokemi och biofysik, 2005. 79 p.
National Category
Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
urn:nbn:se:su:diva-472 (URN)91-7155-024-0 (ISBN)
Public defence
2005-05-13, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 10:00
Available from: 2005-04-21 Created: 2005-04-21Bibliographically approved

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