A New Purification Scheme for Elongation Factor 1 from Rabbit Reticulocytes and Investigation of the Homology of the Subunits with Those of Initiation Factor 2

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Abstract
The subunits of the elongation factor EF-1 and the initiation factor eIF-2 from rabbit reticulocytes were compared. A simple procedure was devised for the purification of EF-1: stepwise chromatography on heparin-Sepharose, separation of the heavy form by sucrose gradient centrifugation, and a final step of stepwise chromatography on RNA-Sepharose. The heparin-Sepharose column also clearly separated EF-1 and EF-2 within 1 chromatographic step. The EF-1 was 350-fold purified and the yield was 10%. After electrophoresis on polyacrylamide gels in the presence of sodium dodecyl sulfate the preparation showed 3 bands corresponding to those described by others as the subunits, with MW of 54,000, 49,000 and 29,200. An additional band of MW 34,000 was present but no others. The 49,000 MW and 34,000 MW bands corresponded exactly in MW to 2 of 3 subunits of eIF-2. A more detailed comparison was therefore made of all subunits of EF-1 and eIF-2. This was done by examination of chymotryptic fingerprints on polyacrylamide gel electrophoresis. No evidence for homology between EF-1 and eIF-2 was found. The 2 larger subunits of eIF-2 had a majority of chymotryptic fragments in common, thus indicating some homology between these polypeptides.