A 23.8-kD alpha-zein with N-terminal sequence and immunological properties similar to 26.7-kD alpha-zeins

A 23.8-kD alpha-zein polypeptide, K55PC7, has been shown to be a truncated member of the 26.7-kD alpha-zein class based on its amino acid composition, N-terminal sequence, and immunological properties. This unusual polypeptide was isolated by chromatographing whole alpha-zein from inbred K55. The N-terminal sequence of K55PC7 is highly homologous to those of 4 putative 26.7-kD alpha-zeins but shows no homology to those of 10 putative alpha-zeins that belong to the 23.8-kD class. Its higher valine and lower phenylalanine contents also suggest that K55PC7 is a member of the 26.7-kD class. In addition, studies with antibodies raised to peptides corresponding to regions unique to each of the two alpha-zein classes indicate that K55PC7 has immunological similarity to 26.7-kD alpha-zeins. Peptide mapping data suggest that K55PC7 is not the putative product of the truncated 26.7-kD alpha-zein gene zA1 isolated from inbred W64A and described by Spena et al. [26]. It appears that K55PC7 occurs as a major component in inbred K55 and is a truncated version of a 26.7-kD alpha-zein, arisen either by an internal deletion or premature termination due to a nonsense mutation.