After removal of cytoplasmic sector F1 from submitochondrial particles of FoF1-ATP synthase complex with guanidine hydrochloride, the transmembrane sector Fo was specifically extracted from the stripped membranes in the presence of detergent CHAPS and partially purified.Two-dimensional crystals were produced by the reconstitution of the partially purified Fo into asolectin and microdialysis. The obtained crystals are able to diffract to 2 nm. The projection map of the negatively stained crystal shows that the crystal has p4212 symmetry, lattice constant, a = b = 14.4nm. A unit cell contains four Fo molecules.