Purification, crystallization and preliminary crystallographic analysis of soybean mature glycinin A1bB2

摘要

Glycinin is one of the most abundant storage-protein molecules in soybean seeds and is composed of five subunits (A1aB1b, A1bB2, A2B1a, A3B4 and A5A4B3). A1bB2 was purified from a mutant soybean cultivar containing glycinin composed of only A5A4B3 and A1bB2. At 281 K the protein formed hexagonal, rectangular and rod-shaped crystals in the first [0.1 M imidazole pH 8.0, 0.2 M MgCl2, 35%(v/v) MPD], second [0.1 M sodium citrate pH 5.6, 0.2 M ammonium acetate, 30%(v/v) MPD] and third (0.1 M phosphate-citrate pH 4.2, 2.0 M ammonium sulfate) crystallization conditions, respectively. X-ray diffraction data were collected to resolutions of 1.85, 1.85 and 2.5 angstrom from crystals of the three different shapes. The crystals belonged to space groups P6(3)22, P2(1) and P1, with unit-cell parameters a = b = 143.60, c = 84.54 angstrom, a = 114.54, b = 105.82, c = 116.67 angstrom, beta = 94.99 degrees and a = 94.45, b = 94.96, c = 100.66 angstrom, alpha = 107.02, beta = 108.44, gamma = 110.71 degrees, respectively. One, six and six subunits of A1bB2 were estimated to be present in the respective asymmetric units. The three-dimensional structure of the A1bB2 hexamer is currently being determined.