TheatpBandatpF genes ofPropionigenium modestumwere cloned as His-tag fusion constructs and expressed in Escherichia recombinant subunits a and b were purified via Ni 2+ chelate affinitychromatography. A func-tionallyactive Focomplex was reassembledin vitro from subunits a, band c, and incorporated into liposomes.