CRYSTALLIZATION AND PRELIMINARY-X-RAY ANALYSIS OF SOYBEAN PROGLYCININS MODIFIED BY PROTEIN ENGINEERING

Glycinin is one of the most abundant storage proteins in soybean seeds . We earlier reported the preparation of proglycinins modified by prot ein engineering to improve food functions. Crystals of the modified pr oglycinins (Delta I, Delta V8, IV+4Met, V+4Met, Gly12, and Ser88) expr essed in Escherichia coli were grown, each under different suitable cr ystallization conditions. The crystals of Delta I, V+4Met, Gly12, and Ser88 diffracted X-rays sufficiently for crystallographic analysis. De lta I, Gly12, and Ser88 crystals were tetragonal, space group P4(1) or P4(3), and with unit cell dimensions a=b=114.3-115.9 Angstrom and c=1 45.1-146.1 Angstrom. V+4Met crystals were monoclinic, space group P2, and with unit cell dimensions a=118.7 Angstrom Angstrom, b = 78.1 Angs trom, c = 109.9 Angstrom, and beta = 119 degrees. The number of protom ers per asymmetric unit of all of the crystals of these four modified proglycinins was about 3. This value is consistent with proglycinins b eing trimers. These data indicated that most of the modified proglycin in crystals examined here could be studied by X-ray crystallography to elucidate the relationships between the structure and the functional properties of glycinin at molecular level.