SMALL-ANGLE X-RAY-SCATTERING STUDIES ON CELLOBIOSE DEHYDROGENASE FROMPHANEROCHAETE-CHRYSOSPORIUM

Limited proteolysis of cellobiose dehydrogenase (CDH) from the white r ot fungus Phanerochaete chrysosporium by papain cleaves the enzyme int o two fragments containing flavin (FAD) and heme, respectively. Small- angle X-ray scattering (SAXS) was employed to investigate size and sha pe of intact CDH and of its fragments in solution. The largest dimensi on of CDH amounts to about 18 nm, whereas the corresponding quantity o f each of the two fragments is only around 9 nm. CDH as well as its fr agments appear to be of prolate shape, the cross-section of the FAD fr agment (diameter 4.3 to 5.1 nm) being considerably larger than that of the heme fragment (diameter 3.3 nm). These findings suggest a colline ar arrangement of the two domains in the CDH particle. Simulations bas ed on the method of finite elements corroborate this structure model a nd furthermore suggest the existence of a possibly flexible linker bet ween the two domains.