Crystal structure of CAXII. Human carbonic anhydrase XII was crystallized at pH 7.5. Diffraction results of CAXII at 1.55 Å resolution suggested that the crystals belong to space group C2 with unit dimensions a=1.46.7 Å, b=44.6 Å, c=85.2 Å, and B=94.1 Å. One homodimer occupied the asymmetric unit. The native structure of CAXII consists of a dimer containing two zinc atoms, two Zn bound acetate ions, and 537 water molecules (9), Copyright 2001.