Structure of a xanthine oxidase-related 4-hydroxybenzoyl-CoA reductase with an additional [4Fe-4S] cluster and an inverted electron flow |
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Authors: | Unciuleac Mihaela Warkentin Eberhard Page Christopher C Boll Matthias Ermler Ulrich |
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Institution: | 1. Institut für Biologie II, Mikrobiologie Schänzlestrasse 1, D-79104 Freiburg, Germany;2. Max-Planck-Institut für Biophysik, Marie-Curie-Strasse 15, D-60439 Frankfurt, Germany;3. The Johnson Research Foundation and Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104 USA |
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Abstract: | The Mo-flavo-Fe/S-dependent heterohexameric protein complex 4-hydroxybenzoyl-CoA reductase (4-HBCR, dehydroxylating) is a central enzyme of the anaerobic degradation of phenolic compounds and belongs to the xanthine oxidase (XO) family of molybdenum enzymes. Its X-ray structure was established at 1.6 A resolution. The most pronounced difference between 4-HBCR and other structurally characterized members of the XO family is the insertion of 40 amino acids within the beta subunit, which carries an additional 4Fe-4S] cluster at a distance of 16.5 A to the isoalloxazine ring of FAD. The architecture of 4-HBCR and concomitantly performed electron transfer rate calculations suggest an inverted electron transfer chain from the donor ferredoxin via the 4Fe-4S] cluster to the Mo over a distance of 55 A. The binding site of 4-hydroxybenzoyl-CoA is located in an 18 A long channel lined up by several aromatic side chains around the aromatic moiety, which are proposed to shield and stabilize the postulated radical intermediates during catalysis. |
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