Structure and Expression of Zein Genes in Maize Endosperm

Abstract

The storage proteins of maize seed are a group of alcohol-soluble proteins called zeins. These proteins can be separated by SDS polyacrylamide gel electrophoresis into four major groups that have apparent mol wts of 22,000, 19,000, 15,000 and 10,000 (Lee et al., 1976; Gianazza et al., 1977). The Mr 22,000 and Mr 19,000 components are made up of several polypeptides. Their NH₂-terminal sequences are heterogeneous (Larkins et al., 1980) and on 2-dimensional polyacrylamide gels they show substantial charge heterogeneity (Hagen and Rubenstein, 1981). The Mr 15,000 and Mr 10,000 polypeptides are less heterogeneous, and appear to consist of only one or two proteins (Hurkman et al., 1981). Charge heterogeneity among different zeins is genotype specific (Righetti et al., 1977) and has been shown in several instances to be inherited in a simple Mendelian fashion (Soave et al., 1978). These studies suggest that the zeins are a highly homologous group of proteins encoded by multiple and closely related genes.