ROLE OF STRUCTURAL DOMAINS FOR MAIZE GAMMA-ZEIN RETENTION IN XENOPUS-OOCYTES

In order to examine the role of cysteine (Cys)-rich domains in the acc umulation of maize (Zea mays L.) gamma-zein within the endoplasmic-ret iculum-derived protein bodies, we studied the localization of gamma-ze in and of two truncated forms of gamma-zein in Xenopus leavis oocytes. The two derivatives were constructed from a DNA encoding the gamma-ze in: one by deletion of the Pro-X linker region (21 amino acids) and th e other by deletion of the Cys-rich domain (94 amino acids). In-vitro- synthesized transcripts were injected into oocytes and the distributio n of the translation products was then analyzed. The entire gamma-zein and both truncated forms of the gamma-zein had accumulated efficientl y in microsomes and no traces of secretion were observed. We suggest t hat neither C-terminal Cys-rich nor Pro-X domains are essential for ga mma-zein retention in oocyte vesicles. Therefore, structural features derived from disulphide bonds are not necessary for gamma-zein targeti ng on the endoplasmic reticulum.