title: Structure of a xanthine oxidase-related 4-hydroxybenzoyl-CoA reductase with an additional [4Fe-4S] cluster and an inverted electron flow.
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.
authors.affiliation: Institut für Biologie II, Mikrobiologie Schänzlestrasse 1, D-79104 Freiburg, Germany.
authors.forename: Mihaela
authors.initials: M
authors.lastname: Unciuleac
authors.forename: Eberhard
authors.initials: E
authors.lastname: Warkentin
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Page
authors.forename: Matthias
authors.initials: M
authors.lastname: Boll
authors.forename: Ulrich
authors.initials: U
authors.lastname: Ermler
mesh_terms: D001665:Binding Sites; D003460:Crystallization; D007501:Iron / Q000378:metabolism*; D008958:Models, Molecular; D008982:Molybdenum / Q000378:metabolism; D010084:Oxidation-Reduction; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D013455:Sulfur / Q000378:metabolism*; D014969:Xanthine Oxidase / Q000737:chemistry*
chemical_list: D013455:Sulfur; D008982:Molybdenum; D007501:Iron; D014969:Xanthine Oxidase; D044925:Oxidoreductases Acting on CH-CH Group Donors; C060482:benzoyl-coenzyme A-4-oxidoreductase