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Unprecedented pathway of reducing equivalents in a diflavin-linked disulfide oxidoreductase

DOI: 10.1073/pnas.1713698114 DOI Help

Authors: Ruben M. Buey (Universidad de Salamanca) , Juan B. Arellano (Consejo Superior de Investigaciones Científicas (CSIC)) , Luis López-maury (Universidad de Sevilla-CSIC) , Sergio Galindo-trigo (Consejo Superior de Investigaciones Científicas (CSIC)) , Adrián Velázquez-campoy (Universidad de Zaragoza; Aragon Institute for Health Research; Biomedical Research Networking Centre for Liver and Digestive Diseases; Fundación Aragonesa para la Investigación y Desarrollo) , José L. Revuelta (Universidad de Salamanca) , Jose M. De Pereda (CSIC-Universidad de Salamanca) , Francisco J. Florencio (Universidad de Sevilla-CSIC) , Peter Schürmann (Université de Neuchâtel) , Bob B. Buchanan (University of California) , Monica Balsera (Consejo Superior de Investigaciones Científicas (CSIC))
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Proceedings Of The National Academy Of Sciences , VOL 264

State: Published (Approved)
Published: November 2017
Diamond Proposal Number(s): 10121

Abstract: Flavoproteins participate in a wide variety of physiologically relevant processes that typically involve redox reactions. Within this protein superfamily, there exists a group that is able to transfer reducing equivalents from FAD to a redox-active disulfide bridge, which further reduces disulfide bridges in target proteins to regulate their structure and function. We have identified a previously undescribed type of flavin enzyme that is exclusive to oxygenic photosynthetic prokaryotes and that is based on the primary sequence that had been assigned as an NADPH-dependent thioredoxin reductase (NTR). However, our experimental data show that the protein does not transfer reducing equivalents from flavins to disulfides as in NTRs but functions in the opposite direction. High-resolution structures of the protein from Gloeobacter violaceus and Synechocystis sp. PCC6803 obtained by X-ray crystallography showed two juxtaposed FAD molecules per monomer in redox communication with an active disulfide bridge in a variant of the fold adopted by NTRs. We have tentatively named the flavoprotein “DDOR” (diflavin-linked disulfide oxidoreductase) and propose that its activity is linked to a thiol-based transfer of reducing equivalents in bacterial membranes. These findings expand the structural and mechanistic repertoire of flavoenzymes with oxidoreductase activity and pave the way to explore new protein engineering approaches aimed at designing redox-active proteins for diverse biotechnological applications.

Journal Keywords: flavoprotein; transfer of reducing equivalents; redox active disulfide; Rossmann fold; sulfhydryl

Subject Areas: Biology and Bio-materials

Instruments: I03-Macromolecular Crystallography

Other Facilities: ALBA Synchrotron