Isolation and characterization of the major fraction (12 S) of linseed proteins

The major protein of linseed, accounting for 66% of the total proteins, was isolated to homogeneity by gel filtration on Sepharose 6B. The protein has an s20,w value of 12 and contained less than 0.5% carbohydrate and no phosphorus. It has an absorption max. at 280 nm and fluorescence emission max. at 320 nm. Circular dichroism studies revealed the protein contained 3% alpha-helix, 17% beta-structure, and the rest aperiodic structure. The 12 S protein showed 5 nonidentical subunits on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE) and 6 subunits each on urea-PAGE in acid and alkaline systems. The intrinsic viscosity value was 3.1 ml/g. Mol. wt. estimated by the Archibald method and sedimentation-diffusion measurements was around 294 000. The protein was found to dissociate at acid pH and in low ionic strength buffers.