Isolation and characterisation of a major seed albumin

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Abstract
The albumin fraction of the seeds of winged bean Psophocarpus tetragonolobus (L.) DC contains the antinutritional factors and several other proteins that are significant components of the total seed protein (˜ 30%). The major protein in the albumin fraction, designated winged bean albumin 1 (WBA 1), was purified to homogeneity by chromatography on Ultrogel AcA 44 and SP‐Sephadex C‐25. WBA 1 crystallized as small needles from a solution of 0.05 M citrate buffer, pH 5.1, on standing at 4°C and was recrystallized to yield larger needles at room temperature. WBA 1 was composed of a single polypeptide chain of Mr 17, 500 which partly associated to a dimer in 5 mM phosphate 0.15 M NaCl, pH 7.0. The amino acid composition of WBA 1 showed a relatively low content of sulfur‐containing amino acids: methionine (1%) and half‐cystine (1%). The amino terminal sequence was found to be homologous with an internal region of vicilin, β conglycinin and phaseolin suggesting a relationship between WBA 1 and the 7S seed globulins.