[Comparison of eukaryotic and prokaryotic elongation factors: isoelectric points and molecular masses]

Using the O'Farrell method, a two-dimensional analysis of RNA-binding proteins from rabbit reticulocytes was carried out. The latter have been shown to consist of several scores of polypeptides, predominantly of a moderately basic type with isoelectric points ranging from 7 to 9.5. The two main components of RNA-binding proteins have been identified as eukaryotic elongation factors EF-1L and EF-2. The RNA-binding elongation factors in eukaryotes have higher isoelectric points and somewhat higher molecular masses as compared to their functional analogs from prokaryotes EF-Tu and EF-G having no affinity for RNA. These results are compatible with the assumption that a nonspecific RNA-binding ability of elongation factors in eukaryotes could have arisen in the course of evolution due to the appearance of an additional RNA-binding "domain" of an alkaline type.