Purification, crystallization, and preliminary X-ray characterization of a36 kDa amaranth globulin

The purpose of this study was to purify, crystallize, and characterize by X -ray diffraction an amaranth globulin for its subsequent structure elucidat ion. A 36-kDa amaranth globulin was extracted by sequential precipitation a nd purified by gel filtration and cationic exchange columns. It was crystal lized at 18 degrees C from 4 hi sodium formate. Suitable crystals for X-ray analysis were found to belong to the tetragonal crystal system with cell d imensions of a = b = 195.5 Angstrom and c = 164.14 Angstrom. Two possible t etragonal space groups P4(1)2(1)2 or P4(3)2(1)2 were determined. The crysta ls diffracted up to 2.5 Angstrom.