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 the ribosomal wash and the postribosomal supernatant of rabbit reticulocytes. A comparison is made between these preparations regarding yield and specific activity. Factors 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.