Crystallization and preliminary X-ray crystallographic studies on Type III antifreeze protein

Type III antifreeze protein, more specifically the recombinant QAE-Sephadex-binding isoform, has been crystallized in 50-55% saturated ammonium sulfate, 0.1 M sodium acetate, pH 4.0-4.5. The resultant crystals belong to the orthorhombic space group P212121 with a = 32.60 A, b = 39.00 A, and c = 46.57 A and diffract to at least 1.7 A. A set of 1.7-A native data has been collected, with completeness 93.4% and Rsym of 0.069. Initial screening for heavy-atom derivatives has yielded a Pt-bound derivative.