The penultimate step of prokaryotic coenzyme A (CoA) biosynthesis is directed by the essential enzyme phosphopantetheine adenylyltransferase (PPAT; EC 22.214.171.124), an attractive target for antibiotics. The reaction catalyzed by PPAT is rate-limiting and involves the transfer of an adenylyl group from ATP to 4'-phosphopantetheine to form 3'-dephospho-CoA. Rhombohedral crystals of PPAT from Mycobacterium tuberculosis (Rv2965c) were obtained. The crystals belong to space group R32, with unit-cell parameters a = 68.69 A, alpha = 91.81 degrees. The crystals diffract to better than 2 A resolution on a Cu Kalpha rotating-anode generator. The packing density for one polypeptide chain in the asymmetric unit is 2.89 A(3) Da(-1), with a solvent content of 0.57.