Phosphopantetheine adenylyltransferase (PPAT, E.C. 188.8.131.52) catalyzes the penultimate step in coenzyme A (CoA) biosynthesis, transferring an adenylyl group from ATP to 4'-phosphopantetheine, and forming dephospho-CoA. Cubic crystals of native PPAT from Escherichia coli as well as PPAT in complex with its substrates were obtained. The crystals belong to space group I23 or I213 with unit-cell dimension a = 135.5 A. The crystals diffract to better than 1.8 A resolution on a Cu Kalpha rotating-anode generator. The asymmetric unit is likely to contain two molecules, corresponding to a packing density of 2.9 A3 Da-1.