Isolation and characterization of .alpha.-globulin of sesame seed (Sesamum indicum L.)

alpha-globulin, the major protein fraction of sesame seeds, was isolated from hexane-extracted seeds and its physical and chemical properties were investigated. alpha-globulin was isolated by extraction of defatted flour with 0.02M phosphate buffer containing 1M NaCl, selective precipitation by dilution with H2O and redissolving the precipitate in extraction buffer. The preparation was 95% homogeneous by the criteria of sedimentation velocity patterns, polyacrylamide gel electrophoresis, DEAE-cellulose chromatography and gel filtration on Sepharose 6B-100. alpha-globulin has a sedimentation velocity of 11S, mol. wt. 250 000 and N content 15.9% and is an oligomer of 12 subunits. The amino acid composition is reported; alpha-globulin contains large amounts of glutamic acid, arginine and aspartic acid (19.98, 14.18 and 9.63 g/100 g protein, resp.).