Interdomain electron transfer in cellobiose dehydrogenase is governed by surface electrostatics

Publication date: Available online 13 November 2016
Source:Biochimica et Biophysica Acta (BBA) - General Subjects
Author(s): Alan Kadek, Daniel Kavan, Julien Marcoux, Johann Stojko, Alfons K.G. Felice, Sarah Cianférani, Roland Ludwig, Petr Halada, Petr Man
BackgroundCellobiose dehydrogenase (CDH) is a fungal extracellular oxidoreductase which fuels lytic polysaccharide monooxygenase with electrons during cellulose degradation. Interdomain electron transfer between the flavin and cytochrome domain in CDH, preceding the electron flow to lytic polysaccharide monooxygenase, is known to be pH dependent, but the exact mechanism of this regulation has not been experimentally proven so far.MethodsTo investigate the structural aspects underlying the domain interaction in CDH, hydrogen/deuterium exchange (HDX-MS) with improved proteolytic setup (combination of nepethesin-1 with rhizopuspepsin), native mass spectrometry with ion mobility and electrostatics calculations were used.ResultsHDX-MS revealed pH-dependent changes in solvent accessibility and hydrogen bonding at the interdomain interface. Electrostatics calculations identified these differences to result from charge neutralization by protonation and together with ion mobility pointed at higher electrostatic repulsion between CDH domains at neutral pH. In addition, we uncovered extensive O-glycosylation in the linker region and identified the long-unknown exact cleavage point in papain-mediated domain separation.ConclusionsTransition of CDH between its inactive (open) and interdomain electron transfer-capable (closed) state is shown to be governed by changes in the protein surface electrostatics at the domain interface. Our study confirms that the interdomain electrostatic repulsion is the key factor modulating the functioning of CDH.General significanceThe results presented in this paper provide experimental evidence for the role of charge repulsion in the interdomain electron transfer in cellobiose dehydrogenases, which is relevant for exploiting their biotechnological potential in biosensors and biofuel cells.

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