Abstract:
A study was made to elucidate the three dimensional structure of soybean glydnin which is one of the
dominant storage proteins of soybean seeds. Previously, the twodisulphide bonds Cys12-Cys45 and
Cys88-Cys298 in the proglydnin AlaBlb subunit were deleted andCys residues were replaced by Gly
and Ser by Oligonucleotide-directed mutagenesis. The mutant proglycinins Gly12, and Ser88 showed
to have better gelation and emulsifying properties. The mutant proglydnins were crystallised along
with the normal proglycinin (AlaBlb -3) and subjected to X-ray structure analysis in an attempt to
determine their structure-junction relationships. The crystals diffracted X-ray to a resollttion limit of
2.9 - 3.4A on stillphotographs and belongto the tetragonal system, space group P41 or P43 with cell
dimensions of a = b·= 114.3 - 115.2A. and d;= 145.7 - 147.1A with 3 protomers per asymmetric
unit. Further refinement data for the' crystals of normal prpglycinin were obtained by multiple
isomorphous replacement and solvent flattening techniques. The tri1?ler dimensions of tlie normal
proglydnin as determined at 6A were 93A by 93A with·the thickness of 36A.
