Isolation and characterization of the major protein fraction of sunflower seeds.

The major protein fraction in sunflower seeds was isolated in a form judged homogeneous by gel filtration, gel electrophoresis and ultracentrifugation. Sunflower meal was extracted with 10% NaCl solution, and after centrifugation the supernatant was fractionated by (NH4)2SO4 precipitation; the fraction precipitating between 6.5 and 13% saturation was dissolved in 1M NaCl and dialysed against 0.025M Tris-glycine buffer pH 8.3. Sedimentation value of the isolated protein was 11.6S; mol. wt. was 300 000. The protein consisted of at least 10 major subunits as judged by sodium dodecyl sulphate polyacrylamide gel electrophoresis. The isolated 11.6S protein contain no P, 0.31% carbohydrate, 0.31% chlorogenic acid and 2 SH groups/300 000 mol. wt. unit. 1 SH group was normally not exposed to sulphydryl reagents in the native state. Information on molecular conformation from circular dichroism studies is also presented.