Isolation and Characterization of 7S Protein-I of Phaseolus angularis (Adzuki bean)

Abstract

The major storage protein of Phaseolus angularis, 7S protein-I, was purified by gel filtration on Sephadex G–200 and ion exchange chromatography on DEAE-cellulose. The purified 7S protein-I was homogeneous on disc electrophoresis, isoelectric focusing and ultracentrifugation. The sedimentation coefficient (, w) and Stokes radius of 7S protein-I were estimated to be 7.5 S and 48 Å, respectively. The molecular weight of 7S protein-I was calculated to be 150,000 ± 15,000 from these values. Polyacrylamide gel electrophoresis of 7S protein-I in the presence of sodium dodecyl sulfate showed one main (55,000 ± 3000 daltons) and two minor protein bands (28,000 ± 1400 and 25,000 ± 1300 daltons). 7S protein-I contained large amounts of glutamic acid and aspartic acid but no cysteine and low amounts of methionine. Carbohydrate analysis of 7S protein-I revealed the presence of 5.0% of neutral sugars and 0.5 % of amino sugars. Circular dichroism measurements indicated that this protein is a β-form rich protein.