Differential translation of rat liver albumin messenger RNA in a wheat germ cell-free system

Abstract

Rat liver polysomal RNA directs the synthesis of albumin in a wheat germ cell-free system. The in vitro product has the same mobility in polyacrylamide-sodium dodecyl sulfate gels as purified rat liver albumin and can be immune precipitated with rabbit anti-rat liver albumin serum. The incorporation of [35S]methionine into total protein in an in vitro system increased linearly with increasing messenger RNA concentration until a saturation plateau was reached. The synthesis of albumin compared to total protein increased continually with increasing RNA concentration. Addition of the polynucleotide poly(A) to the cell-free system inhibited incorporation, presumably through interference with the initiation process, and increased the relative albumin synthesis. Translation of albumin mRNA was also resistant to inhibition by high levels of potassium acetate where total incorporation was cut in half. The results suggest that the mRNA for albumin, in addition to the mRNA for the .beta. chain of globin and for the immunoglobulin polypeptides, is particularly efficient in initiating protein synthesis.