Université Grenoble Alpes, BIG-LCBM, Grenoble, France, CNRS, BIG-LCBM, Grenoble, France, CEA, BIG-LCBM, Grenoble, France, Université Grenoble Alpes, DCM UMR 5250, Grenoble, France, CNRS, DCM UMR 5250, Grenoble, France, Université Grenoble Alpes, INAC-SPrAM, Grenoble, France, CNRS, INAC-SPrAM, Grenoble, France, CEA, INAC-SPrAM, Grenoble, France, ERRMECe, I-MAT FD4122, Université de Cergy-Pontoise, 2 Avenue Adolphe Chauvin, Cergy-Pontoise Cedex, France, LMGP, CNRS UMR 5628, 3 parvis Louis Néel, Grenoble, France, Institut Néel, CNRS-UJF-INP, Grenoble Cedex 09, France, Laboratoire de Chimie des Processus Biologiques, UMR 8229 CNRS, Université Pierre et Marie Curie - Paris 6, Collège de France, 11 Place Marcelin Berthelot, Paris Cedex 05, France, CEA, LETI, MINATEC Campus, Grenoble, France, Department of Chemical Engineering, University of Bath, Bath, United Kingdom, Nagoya Institute of Technology, Frontier Research Institute, Nagoya, Aichi, Japan

Engineering bioelectronic components and set-ups that mimic natural systems is extremely challenging. Here we report the design of a protein-only redox film inspired by the architecture of bacterial electroactive biofilms. The nanowire scaffold is formed using a chimeric protein that results from the attachment of a prion domain to a rubredoxin (Rd) that acts as an electron carrier. The prion domain self-assembles into stable fibres and provides a suitable arrangement of redox metal centres in Rd to permit electron transport. This results in highly organized films, able to transport electrons over several micrometres through a network of bionanowires. We demonstrate that our bionanowires can be used as electron-transfer mediators to build a bioelectrode for the electrocatalytic oxygen reduction by laccase. This approach opens opportunities for the engineering of protein-only electron mediators (with tunable redox potentials and optimized interactions with enzymes) and applications in the field of protein-only bioelectrodes. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.