Polymorphism in fowl serum albumin VII. Distribution and activity of free and membrane-bound polysomes in developing fowl liver

Abstract

The quantity and activities of membrane-bound and free polysomes in livers from chick embryos at successive stages of development were compared in cell-free protein-synthesizing systems. Membrane-bound polysomes increased 2-fold between 8 and 18 days of development, while total polyribosome content remained constant. Free polysome activity also remained constant during this period, while that of membrane-bound (total — free) polysomes decreased, possibly because of an increase in ribonuclease activity in this fraction. Serum albumin biosynthesis occurred primarily on membrane-bound polysomes. With liver development, increased secretion of serum proteins may be correlated with synthesis of serum albumin on increasing numbers of membrane-bound polyribosomes.