A non-catalytic N-terminal domain negatively influences the nucleotide exchange activity of translation elongation factor 1Bα

Eukaryotic translation elongation factor 1B (eEF1B) is a functional homolog of the bacterial factor EF-Ts, and is a component of the macromolecular eEF1B complex. eEF1B functions as a catalyst of guanine nucleotide exchange on translation elongation factor 1A (eEF1A). The C-terminal domain of eEF1B is necessary and sufficient for its catalytic activity, whereas the N-terminal domain interacts with eukaryotic translation elongation factor 1B (eEF1B) to form a tight complex. However, eEF1B has been shown to enhance the catalytic activity of eEF1B attributed to the C-terminal domain of eEF1B. This suggests that the N-terminal domain of eEF1B may in some way influence the guanine nucleotide exchange process. We have shown that full-length recombinant eEF1B and its truncated forms are non-globular proteins with elongated shapes. Truncation of the N-terminal domain of eEF1B, which is dispensable for catalytic activity, resulted in acceleration of the rate of guanine nucleotide exchange on eEF1A compared to full-length eEF1B. A similar effect on the catalytic activity of eEF1B was observed after its interaction with eEF1B. We suggest that the non-catalytic N-terminal domain of eEF1B may interfere with eEF1A binding to the C-terminal catalytic domain, resulting in a decrease in the overall rate of the guanine nucleotide exchange reaction. Formation of a tight complex between the eEF1B and eEF1B N-terminal domains abolishes this inhibitory effect.