Translation of the mRNAs coding for the major hemolymph proteins of Ceratitis capitata in cell-free system: Comparison of the translatable mRNA levels to the respective biosynthetic levels of the proteins in the fat body during development

Four major hemolymph polypeptides (ceratitins) with molecular weights between 8.1 × 10 4 and 8.7 × 10 4 daltons have been identified in the fat body of late Ceratitis capitata larvae. Total fat body RNA from late larvae was translated in reticulocyte lysate, and the predominant in vitro translation products were shown to be the ceratitin precursors. The biosynthesis of these proteins during postembryonic development was studied in both tissue culture and cell-free system. Comparison of the biosynthetic patterns obtained in the two systems suggests a linear relationship between messenger concentration and protein synthesis. Three of these polypeptides show a coordinate pattern of synthesis and are immunologically related. After pupation, all four ceratitins are reabsorbed by the fat body where they accumulate.