Herein, the electron-transfer reactions occurring at the interface between bilirubin oxidase (BOD) and nanocrystalline hematite (alpha-Fe2O3) were characterized. Cyclic voltammograms indicated that BOD has an affinity for hematite surfaces and establishes a direct electron-transfer (DET) conduit between the primary electron acceptor T1 site and the conduction band of a-Fe2O3. DET was also confirmed photo-electrochemically, as cathodic photocurrents were generated when a nanocomposite of BOD and alpha-Fe2O3 was illuminated under oxygenated conditions. A proline residue displayed a high-binding affinity for hematite surfaces and is therefore likely part of an orientation-controlled motif which serves to locate BOD at the T1 site at a suitable distance for DET to alpha-Fe2O3. (C) 2010 Elsevier B.V. All rights reserved.