PRELIMINARY CRYSTALLOGRAPHIC ANALYSIS OF SWEET-POTATO BETA-AMYLASE

Beta amylase from sweet potato has been crystallized in a form suitable for high resolution X-ray diffraction analysis from a mixture of polyethylene glycol 400 and ammonium sulfate at room temperature. The crystals are rectangular prisms and occasionally reach a size of 1 mm on an edge. The space group of the crystals is I422 with cell dimensions of a = b = 196.4 AÅ and c = 72.2 AÅ. There are four tetramers of about Mr = 210,000 in the unit cell centered at 222 symmetry points. The asymmetric unit is a single beta amylase subunit of about Mr = 52,000. The tetrameric molecule must have exact 222 molecular symmetry relating its subunits. © 1993 Academic Press, Inc.