Electron Transfer to Light-Activated Photosynthetic Reaction Centers from Rhodobacter sphaeroides Reconstituted in a Biomimetic Membrane System

Photosynthetic reaction centers (RCs) from Rb. sphaeroides with a genetically engineered 7-his-tag at the C-terminus of the M-subunit are bound to a Ni-NTA-modified gold surface. Subsequently, the bound RCs are subjected to in situ dialysis in the presence of lipid micelles to form a protein-tethered lipid bilayer membrane (ptBLM). Redox properties of the RC thus immobilized are investigated by cyclic voltammetry. Photocurrrents are generated in the range of 10 μA cm–2, however, different from previous studies at potentials of −200 and −300 mV, and without cytochrome c as a mediator. The unexpected behavior is explained in terms of an interprotein reaction between RC molecules promoted by the lipid bilayer, which we had previously detected by surface-enhanced infrared absorption spectroscopy.