Cell-free synthesis of preuteroglobin and processing to uteroglobin by polysomes from rabbit endometrium

Polysomes from rabbit endometrium, incubated in a cell-free system in the presence of [35S]methionine, completed polypeptide chains pre-initiated in vivo. Polypeptide chains were analyzed by SDS-gel electrophoresis after immunoprecipitation with anti-uteroglobin. Endometrial polysomes, freed of membranes by detergent treatment, synthesized both mature uteroglobin and preuteroglobin not yet cleaved in vivo. Membrane-bound polysomes synthesized exclusively mature uteroglobin, indicating the processing of preuteroglobin by the membranes bound to the ribosomes.