Crystallization and preliminary X-ray diffraction studies of the alpha-amylase inhibitor coded 0.19 from wheat kernel.

The alpha-amylase inhibitor coded 0.19 (0.19AI) from wheat kernel is a dimeric protein which inactivates exogenous alpha-amylases. Crystals of 0.19AI were grown at room temperature and pH 7.0 from a protein solution with a low salt concentration. They were trigonal, belonged to space group P3(1) or P3(2), and had unit cell dimensions of a = b = 79.3 A and c = 60.8 A. The crystals diffract X-rays to at least 2.0 A resolution and are stable to X-ray beams. The asymmetric unit appears to contain two 0.19AI dimers. A potential heavy-atom derivative was prepared by soaking the crystal in a HgCl2 solution.