The photosynthetic reaction center complex was immobilized on a p-benzoquinonethiol-modified Au electrode. The potential of the reaction center-immobilized Au electrode in 0.1 M (M = mol/dm(3)) Tris-HCl buffer (pH 7.5) was shifted, upon illumination, to the negative direction, and the value increased with increasing the intensity of incident light. In addition, the potential shift was enhanced by adding cytochrome c(2) to the solution. A photogalvanic cell was constructed only using this electrode, cytochrome c(2), and an ITO electrode with hydrophilic surface, and the cell performance was examined. The open-circuit photovoltage and the short-circuit photocurrent were about 5 mV and 40 nA, respectively.