title: Crystal structure of the flavoprotein domain of the extracellular flavocytochrome cellobiose dehydrogenase.
abstract: Cellobiose dehydrogenase (CDH) participates in the degradation of cellulose and lignin. The protein is an extracellular flavocytochrome with a b-type cytochrome domain (CYT(cdh)) connected to a flavodehydrogenase domain (DH(cdh)). DH(cdh) catalyses a two-electron oxidation at the anomeric C1 position of cellobiose to yield cellobiono-1,5-lactone, and the electrons are subsequently transferred from DH(cdh) to an acceptor, either directly or via CYT(cdh). Here, we describe the crystal structure of Phanerochaete chrysosporium DH(cdh) determined at 1.5 A resolution. DH(cdh) belongs to the GMC family of oxidoreductases, which includes glucose oxidase (GOX) and cholesterol oxidase (COX); however, the sequence identity with members of the family is low. The overall fold of DH(cdh) is p-hydroxybenzoate hydroxylase-like and is similar to, but also different from, that of GOX and COX. It is partitioned into an FAD-binding subdomain of alpha/beta type and a substrate-binding subdomain consisting of a seven-stranded beta sheet and six helices. Docking of CYT(cdh) and DH(cdh) suggests that CYT(cdh) covers the active-site entrance in DH(cdh), and that the resulting distance between the cofactors is within acceptable limits for inter-domain electron transfer. Based on docking of the substrate, cellobiose, in the active site of DH(cdh), we propose that the enzyme discriminates against glucose by favouring interaction with the non-reducing end of cellobiose.
authors.affiliation: Department of Cell and Molecular Biology, Structural Biology, Biomedical Centre, Uppsala University, SE-751 24 Uppsala, Sweden.
authors.forename: B M
authors.initials: BM
authors.lastname: Hallberg
authors.forename: Gunnar
authors.initials: G
authors.lastname: Henriksson
authors.forename: Göran
authors.initials: G
authors.lastname: Pettersson
authors.forename: Christina
authors.initials: C
authors.lastname: Divne
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002237:Carbohydrate Dehydrogenases / Q000737:chemistry* / Q000378:metabolism; D002475:Cellobiose / Q000378:metabolism; D002482:Cellulose / Q000378:metabolism; D018360:Crystallography, X-Ray; D003573:Cytochrome b Group; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020075:Phanerochaete / Q000201:enzymology*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: D003573:Cytochrome b Group; D005182:Flavin-Adenine Dinucleotide; D002475:Cellobiose; D002482:Cellulose; D002237:Carbohydrate Dehydrogenases; C019859:cellobiose-quinone oxidoreductase