beta-Carbonic anhydrase from Pisum sativum: crystallization and preliminary X-ray analysis

Recombinant beta-carbonic anhydrase from the garden pea, Pisum sativum, was purified to homogeneity and crystallized. Crystals belong to the orthorhom bic space group C222, with unit-cell parameters a = 136.3, b = 142.5, c = 2 01.4 Angstrom, alpha = beta = gamma = 90 degrees. Crystals typically diffra cted anisotropically, with a maximal resolution of 2.0 Angstrom in the stro ngest direction. The calculated Matthews parameter predicts approximately e ight molecules in the asymmetric unit, consistent with previous reports of the molecule being an octamer. However, examination of the self-rotation fu nction revealed no fourfold symmetry axis and multiple weak twofold axes pe rpendicular to the crystallographic c axis, indicating that the oligomeriza tion arrangement is not that of a 422 octamer.