Structural basis for cellobiose dehydrogenase action during oxidative cellulose degradation

• Published in: Nature communications Vol. 6; no. 1; p. 7542
• Main Authors: Tan, Tien-Chye, Kracher, Daniel, Gandini, Rosaria, Sygmund, Christoph, Kittl, Roman, Haltrich, Dietmar, Hällberg, B. Martin, Ludwig, Roland, Divne, Christina
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 07.07.2015; Nature Publishing Group; Nature Pub. Group
• Subjects: 631/326/193/2538; 631/45/535; 631/57/2272; BASIC BIOLOGICAL SCIENCES; Biotechnology; Carbohydrate Conformation; Carbohydrate Dehydrogenases - genetics; Carbohydrate Dehydrogenases - metabolism; Catalytic Domain; Cellulose; Cellulose - metabolism; Cloning, Molecular; Copper; Cytochrome; Dehydrogenases; Flavin-Adenine Dinucleotide - metabolism; Fungal Proteins - genetics; Fungal Proteins - metabolism; Fungi; Fungi - enzymology; Fungi - genetics; Fungi - metabolism; Heme - metabolism; Humanities and Social Sciences; Medicin och hälsovetenskap; Models, Molecular; Molecular biology; multidisciplinary; Mutagenesis; Mutagenesis, Site-Directed; Mutation; Protein Binding; Protein Conformation; Science; Science & Technology - Other Topics; Science (multidisciplinary); Sweden; Germany
• DOI: 10.1038/ncomms8542
• ISSN: 2041-1723

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. Cellobiose dehydrogenases (CDHs) cooperate with lytic polysaccharide monooxygenases (LPMOs) to catalyse cellulose degradation. Here Tan et al . define the electron transfer pathway in CDH, providing a structural analysis of CDH conformers and of the interaction between CDH and LPMO during cellulose depolymerisation.