Designed proteins capable of electron transfer are of interest as tools to accomplish many applications including industrial chemical applications, solar energy, and nanochemical therapeutic devices. However, these proteins require a source of electrons and interfacing them with the endogenous electron-providing proteins of a cell is a difficult task. To avoid this compatibility and stoichiometry problem, we take advantage of the natural catalytic function of phthalate dioxygenase reductase, a flavoprotein which transforms the paired reducing equivalents of NADH into sequential single electrons by fusing it to a de novo designed diheme helical bundle domain. This two-part module is intended for use in varied applications such as as a prodrug activating enzyme for cancer therapy or in solar energy conversion.