title: Structural basis for cellobiose dehydrogenase action during oxidative cellulose degradation.
abstract: A new paradigm for cellulose depolymerization by fungi focuses on an oxidative mechanism involving cellobiose dehydrogenases (CDH) and copper-dependent lytic polysaccharide monooxygenases (LPMO); however, mechanistic studies have been hampered by the lack of structural information regarding CDH. CDH contains a haem-binding cytochrome (CYT) connected via a flexible linker to a flavin-dependent dehydrogenase (DH). Electrons are generated from cellobiose oxidation catalysed by DH and shuttled via CYT to LPMO. Here we present structural analyses that provide a comprehensive picture of CDH conformers, which govern the electron transfer between redox centres. Using structure-based site-directed mutagenesis, rapid kinetics analysis and molecular docking, we demonstrate that flavin-to-haem interdomain electron transfer (IET) is enabled by a haem propionate group and that rapid IET requires a closed CDH state in which the propionate is tightly enfolded by DH. Following haem reduction, CYT reduces LPMO to initiate oxygen activation at the copper centre and subsequent cellulose depolymerization.
authors.affiliation: 1] School of Biotechnology, KTH Royal Institute of Technology, AlbaNova University Center, Roslagstullsbacken 21, Stockholm S-10691, Sweden [2] Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Scheelelaboratoriet, Scheeles väg 2, Stockholm S-17177, Sweden.
authors.forename: Tien-Chye
authors.initials: TC
authors.lastname: Tan
authors.affiliation: Food Biotechnology Laboratory, Department of Food Science and Technology, Vienna Institute of Biotechnology (VIBT), BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, Vienna A-1190, Austria.
authors.forename: Daniel
authors.initials: D
authors.lastname: Kracher
authors.affiliation: 1] School of Biotechnology, KTH Royal Institute of Technology, AlbaNova University Center, Roslagstullsbacken 21, Stockholm S-10691, Sweden [2] Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Scheelelaboratoriet, Scheeles väg 2, Stockholm S-17177, Sweden.
authors.forename: Rosaria
authors.initials: R
authors.lastname: Gandini
authors.affiliation: Food Biotechnology Laboratory, Department of Food Science and Technology, Vienna Institute of Biotechnology (VIBT), BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, Vienna A-1190, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Sygmund
authors.affiliation: Food Biotechnology Laboratory, Department of Food Science and Technology, Vienna Institute of Biotechnology (VIBT), BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, Vienna A-1190, Austria.
authors.forename: Roman
authors.initials: R
authors.lastname: Kittl
authors.affiliation: Food Biotechnology Laboratory, Department of Food Science and Technology, Vienna Institute of Biotechnology (VIBT), BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, Vienna A-1190, Austria.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Haltrich
authors.affiliation: 1] Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm S-17177, Sweden [2] European Molecular Biology Laboratory, Hamburg Unit, Hamburg 22603, Germany; and Centre for Structural Systems Biology (CSSB), DESY-Campus, Hamburg 22603, Germany.
authors.forename: B Martin
authors.initials: BM
authors.lastname: Hällberg
authors.affiliation: Food Biotechnology Laboratory, Department of Food Science and Technology, Vienna Institute of Biotechnology (VIBT), BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, Vienna A-1190, Austria.
authors.forename: Roland
authors.initials: R
authors.lastname: Ludwig
authors.affiliation: 1] School of Biotechnology, KTH Royal Institute of Technology, AlbaNova University Center, Roslagstullsbacken 21, Stockholm S-10691, Sweden [2] Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Scheelelaboratoriet, Scheeles väg 2, Stockholm S-17177, Sweden.
authors.forename: Christina
authors.initials: C
authors.lastname: Divne
mesh_terms: D002236:Carbohydrate Conformation; D002237:Carbohydrate Dehydrogenases / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D002482:Cellulose / Q000378:metabolism*; D003001:Cloning, Molecular; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005658:Fungi / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D006418:Heme / Q000378:metabolism; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D005656:Fungal Proteins; D005182:Flavin-Adenine Dinucleotide; D006418:Heme; D002482:Cellulose; D002237:Carbohydrate Dehydrogenases; C019859:cellobiose-quinone oxidoreductase