Cloning of a cDNA encoding cellobiose dehydrogenase, a hemoflavoenzyme from Phanerochaete chrysosporium.
Cellobiose dehydrogenase (CDH) is an extracellular hemoflavoenzyme produced by cellulose-degrading cultures of the wood-degrading basidiomycete Phanerochaete chrysosporium. CDH contains one flavin adenine dinucleotide (FAD) and one heme b per molecule, and it oxidizes cellobiose to cellobionolactone. In this report, a 2.4-kb cDNA encoding CDH was isolated by screening an expression library of P. chrysosporium OGC101 with a CDH-specific polyclonal antibody. The cDNA encodes a 755-amino-acid protein with a predicted mass of 80,115 Da. Sequence analysis suggests that the heme domain is located at the N terminus and that the falvin domain is located at the C terminus. The flavin domain shows a beta 1-alpha A-beta 2 motif for FAD binding and has high sequence similarity to several FAD-dependent enzymes. Little sequence similarity to hemoflavoenzymes is found. CDH binds to cellulose similarly to cellulases. However, little sequence similarity is observed with the conserved cellulose-binding sequences of cellulases. This suggests that CDH might possess a specific sequence for cellulose binding which is different from that of cellulases. Northern (RNA) blot analysis of total RNA from cellulose-, glucose-, and cellobiose-grown P. chrysosporium indicated that CDH mRNA is produced only in cellulose-grown cells. This suggests that CDH expression is regulated at the transcriptional level by either cellulose or one of its degradation products. Southern blot analysis suggests the presence of only a single gene for CDH in P. chrysosporium OGC101.
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Department of Chemistry, Biochemistry, and Molecular Biology, Oregon Graduate Institute of Science & Technology, Portland 97291-1000, USA.
Nagalla
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Renganathan
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D000595:Amino Acid Sequence; D001483:Base Sequence; D001487:Basidiomycota / Q000201:enzymology* / Q000235:genetics*; D001665:Binding Sites; D002237:Carbohydrate Dehydrogenases / Q000737:chemistry / Q000235:genetics*; D002482:Cellulose; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics*; D004271:DNA, Fungal / Q000235:genetics*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
D017931:DNA Primers; D018076:DNA, Complementary; D004271:DNA, Fungal; D002482:Cellulose; D002237:Carbohydrate Dehydrogenases; C019859:cellobiose-quinone oxidoreductase