Isolation and characterization of a methionine-rich protein from Maize Endosperm

A 17,000 mol. wt methionine-rich (met-rich) polypeptide from alcohol-soluble reduced glutelin (ASG) of maize endosperm from the hybrid WF9 × Br 38 was purified by a combination of differential solubility and ion exchange chromatography. Antiserum specific for this polypeptide was prepared against a similar fraction purified by Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE) from the inbred W64A. This polypeptide (17,000 mol. wt met-rich ASG) is distinct from zein and other ASG fractions in that it contains the highest levels of methionine (10·8 mol%), glycine, alanine, tyrosine and arginine, and the lowest levels of proline, valine, isoleucine, histidine and phenylalanine among these proteins. Its N-terminal sequence, determined for 36 residues, shows numerous dipeptide (Ala-Gly and Gly-Leu) repeats and it shares no homology with either zein or proline-rich ASG fractions; this lack of homology was also indicated by results from immunological studies.