An update on the biophysical character of the human eukaryotic elongation factor 1 beta: Perspectives from interaction with elongation factor 1 gamma

Abstract The β‐subunit of the human eukaryotic elongation factor 1 complex (heEF1β) plays a central role in the elongation step in eukaryotic protein biosynthesis, which essentially involves interaction with the α‐ and γ‐subunits (eEF1γ). To biophysically characterize heEF1β, we constructed 3 Escherichia coli expression vector systems for recombinant expression of the full length (FL‐heEF1β), N‐terminus (NT‐heEF1β), and the C‐terminus (CT‐heEF1β) regions of the protein. Our results suggest that heEF1β is predominantly alpha‐helical and possesses an accessible hydrophobic cavity in the CT‐heEF1β. Both FL‐heEF1β and NT‐heEF1β form dimers of size 62 and 30 kDa, respectively, but the CT‐heEF1β is monomeric. FL‐heEF1β interacts with the N‐terminus glutathione transferase‐like domain of heEF1γ (NT‐heEF1γ) to form a 195‐kDa complex or a 230‐kDa complex in the presence of oxidized glutathione. On the other hand, NT‐heEF1β forms a 170‐kDa complex with NT‐heEF1γ and a high molecular weight aggregate of size greater than 670 kDa. Surface plasmon resonance analysis confirmed that (by fitting the Langmuir 1:1 model) FL‐heEF1β associated with monomeric or dimeric NT‐heEF1γ at a rapid rate and slowly dissociated, suggesting strong functional affinity ( K D = 9.6 nM for monomeric or 11.3 nM for dimeric NT‐heEF1γ). We postulate that the N‐terminus region of heEF1β may be responsible for its dimerization and the C‐terminus region of heEF1β modulates the formation of an ordered heEF1β‐γ oligomer, a structure that may be essential in the elongation step of eukaryotic protein biosynthesis.