MODIFICATION TOLERABILITY OF THE HYPERVARIABLE REGION OF SOYBEAN PROGLYCININ

Glycinin is one of two major storage proteins of soybean seeds. To inv estigate the modification tolerability of the hypervariable region of proglycinin A(1a)B(1b) subunit, chemical properties of the hypervariab le region were changed by deleting a polyglutamic acid sequence in the hypervariable region and substituting it with polylysine, polyglutami ne, and polymethionine sequences. All modified proglycinins were overp roduced in Escherichia coli cells, accumulated as soluble proteins, an d self-assembled into trimers such as native proglycinin. This indicat es that the hypervariable region can tolerate all modifications attemp ted in this study. Modified proglycinins purified to near homogeneity were attempted for crystallization. Although all of the modified progl ycinins were partially limited-proteolyzed in the hypervariable region s, they could form crystals consisting of the two proglycinin molecula r species: intact and limited-proteolyzed. Results suggest that the hy pervariable region of proglycinin forms a flexible structure. It is co ncluded that this flexible structure may be responsible for the modifi cation tolerability of the hypervariable region.