PAT is an acetyltransferase from the archaeon Sulfolobus solfataricus that specifically acetylates the chromatin protein Alba. The enzyme was expressed, purified and subsequently crystallized using the sitting-drop vapour-diffusion technique. Native diffraction data were collected to 1.70 A resolution on the BL13C1 beamline of NSRRC from a flash-frozen crystal at 100 K. The crystals belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 44.30, b = 46.59, c = 68.39 A.