Crystallization and preliminary crystallographic data for oncomodulin

Oncomodulin, a parvalbumin-like calcium-binding protein isolated from rat tumours, has been crystallized from 33% polyethylene glycol 6000 at pH 5·2 in the presence of CaCl 2 and dithiothreitol. The crystals belong to the space group P2 12 12 1, with unit cell dimensions a = 39·59(1) A ̊ , b = 64·28(2) A ̊ and c = 33·07(1) A ̊ , and have one molecule of oncomodulin per asymmetric unit. Their solvent content is only 31% ( v v ) and they are remarkably stable. Three complete sets of data, one to 1·85 Å resolution for the native protein and one to 2·0 Å for each of two heavy-atom derivatives, have been collected. A three-dimensional structure analysis is in progress.