Conformational control of the interaction of eukaryotic elongation factors EF-1 and EF-2 with ribosomes

As in the case with prokaryotic systems, Artemia salina elongation factors EF-1 and EF-2 interact with a common site or with closely overlapping sites on the Artemia ribosome. This feature of ribosomal design must restrict interaction with the ribosome to only one of the factors at alternating steps of chain elongation. In support of this view we find that EF-1, but not EF-2, interacts with the post-translocation ribosome, whereas the reverse is true of the pre-translocation ribosome. Conformational changes probably account for the alternating selectivity of the translating ribosome for each elongation factor.