Immunological cross-reactivity among α-zeins of maize (Zea mays L.)

Abstract

Polyclonal antisera were produced against four different α-zein polypeptides representing Mr -23800, -25000 and -26700 size classes, respectively, as well as a truncated Mr -26700 polypeptide whose size was similar to Mr -23800 polypeptides. Both SDS-denatured and ‘native’ forms of polypeptides were used for immunization. Seven different antisera to intact α-zein polypeptides and one to a synthetic peptide were reacted with each of the different α-zein polypeptides used for immunization and whole α-zein fraction from a maize inbred (K55) in ELISA. The same antisera were used to immunostain whole α-zein blots after SDS-PAGE of inbreds K55 and W64A and also whole zein blots after IEF. The results indicated extensive immunological cross-reactivity among α-zein polypeptides when antisera to denatured immunogens were used in assays, whereas antisera to native immunogens yielded varying degrees of reduced cross-reactivity. Antisera to native immunogens showed little or no reactivity towards some α-zein charge components in IEF blots belonging presumably to a size class different from that of the homologous antigen. The results indicated also that the Mr -25000 α-zein size class was immunologically related more to Mr -26700 than Mr -23800 polypeptides. Likewise, a Mr -23800 α-zein polypeptide from inbred K55 was shown to be a trMr -26700 polypeptide by polyclonal, monoclonal and anti-synthetic peptide antibodies. It is concluded that polyclonal antisera to intact α-zein polypeptides could be used to distinguish polypeptides from different homology classes, but they would be of limited use, if any, in discriminating individual polypeptides within a homology class. Thus, monoclonal antibodies to intact α-zein polypeptides and polyclonal and monoclonal antibodies to synthetic peptides corresponding to sites unique to individual α-zein polypeptides show a greater promise of studying structural relationships among different α-zeins by immunological probes. © 1988, Academic Press Limited. All rights reserved.