Role of structural domains for maize ?-zein retention in Xenopus oocytes

Abstract

In order to examine the role of cysteine (Cys)-rich domains in the accumulation of maize (Zea mays L.) γ-zein within the endoplasmic-reticulum-derived protein bodies, we studied the localization of γ-zein and of two truncated forms of γ-zein in Xenopus laevis oocytes. The two derivatives were constructed from a DNA encoding the γ-zein: one by deletion of the Pro-X linker region (21 amino acids) and the other by deletion of the Cys-rich domain (94 amino acids). In-vitro-synthesized transcripts were injected into oocytes and the distribution of the translation products was then analyzed. The entire γ-zein and both truncated forms of the γ-zein had accumulated efficiently in microsomes and no traces of secretion were observed. We suggest that neither C-terminal Cys-rich nor Pro-X domains are essential for γ-zein retention in oocyte vesicles. Therefore, structural features derived from disulphide bonds are not necessary for γ-zein targeting on the endoplasmic reticulum.