Crystallization and preliminary x-ray crystallographic analysis of spruce budworm antifreeze protein

Antifreeze proteins have the ability to bind to ice with high affinity and inhibit further crystal growth. The insect antifreeze protein from spruce b udworm exhibits very high thermal hysteresis activity and is implicated in the protection of overwintering larvae from freezing. This protein has been crystallized in 20-25% polyethylene glycol (M-r 6000), 0.4 M NaCl, 0.1 M T ris-HCl, pH 8.5, by vapor diffusion using the hanging drop method. The resu lting crystals are very thin (typically <0.01 mm in the shortest dimension) , and only after repeated seeding could crystals be grown large enough for data collection using synchrotron radiation. The crystals belong to the mon oclinic space group C2, with cell dimensions a 82.28 Angstrom, b = 62.29 An gstrom, c = 63.63 Angstrom and beta = 113.7 degrees. Molecules in the asymm etric unit are related by a twofold axis of symmetry with two molecules pre sent. Native data to a resolution of 2.6 Angstrom have been collected with 90.3% completeness and a R-sym of 6.9%. (C) 1999 Academic Press.