A Comparison of the Initiation Factors of Eukaryotic Protein Synthesis from Ribosomes and from the Postribosomal Supernatant

Abstract

A purification procedure is described for the initiation factors of protein synthesis from rabbit reticulocytes: (a) from the ribosomal wash and (b) from the postribosomal supernatant. A comparison is made between these preparations with respect to yield and specific activity. eIF‐4A and eIF‐4D occur mainly in the postribosomal supernatant; eIF‐2, eIF‐4C and eIF‐5 are more evenly divided over both fractions, whereas eIF‐1, eIF‐3 and eIF‐4B are found almost exclusively in the ribosomal wash. No significant difference in specific activity could be detected when factors from both sources were compared, with a possible exception of eIF‐4A and eIF‐4D. Copyright © 1979, Wiley Blackwell. All rights reserved