RATES OF POLYPEPTIDE CHAIN ASSEMBLY IN LIVER IN VIVO: RELATION TO THE MECHANISM OF TEMPERATURE ACCLIMATION IN OPSANUS TAU^*

Abstract

A simple translational model, present herein, permits experimental determination of the rates of protein synthesis in vivo in terms of a time constant representing the average assembly time of the polypeptide chains. The model has been used to interpret incorporation of radioactive amino acids into toadfish liver fractions as a function of time after hepatic portal vein injection. The results suggest that the increase in liver protein synthesis produced by cold acclimation is due to a more rapid rate of addition of amino acid residues to the growing polypeptide chains. The finding is consistent with the greater aminoacyl transferase activity in livers of cold-acclimated fish.