The presence of high molecular weight aggregates in the protein bodies of developing endosperms of wheat and other cereals

Abstract

Protein bodies have been isolated from developing grain of wheat, barley and rye. The protein has been solubilised in a solvent consisting of 0·01- M acetic acid, 6- M urea and 55-m M cetyltrimethylammonium bromide and chromatographed on columns of controlled pore glass. In each case a proportion of the protein was eluted in the excluded volume of the column, indicating the presence of multimeric aggregates in the protein bodies. In all three cereals these aggregates contained an enhanced proportion of high molecular weight polypeptides and certain sulphur-rich prolamins. The proportion of aggregated material in wheat protein bodies was similar to that in gluten preparations and two-dimensional electrophoretic analyses showed that protein bodies and gluten consisted of almost identical polypeptides. We therefore suggest that the aggregates of gluten proteins, which have been implicated as important in determining bread-making quality, are laid down in protein bodies shortly after synthesis in the developing seed. Similar studies have also been carried out with maize protein bodies. Although these contained some aggregated proteins they did not appear to contain the very large complexes observed in the other three cereals.