The protein-binding N-terminal domain of human translation elongation factor 1Bβ possesses a dynamic α-helical structural organization

Translation elongation factor 1B beta (eEF1B beta) is a metazoan-specific protein involved into the macromolecular eEF1B complex, containing also eEF1B alpha and eEF1B gamma subunits. Both eEF1B alpha and eEF1B beta ensure the guanine nucleotide exchange on eEF1A while eEF1B gamma is thought to have a structural role. The structures of the eEF1B beta catalytic C-terminal domain and neighboring central acidic region are known while the structure of the protein binding N-terminal domain remains unidentified which prevents clear understanding of architecture of the eEF1B complex. Here we show that the N-terminal domain comprising initial 77 amino acids of eEF1B beta, eEF1B beta(1-77), is a monomer in solution with increased hydrodynamic volume. This domain binds eEF1B gamma in equimolar ratio. The CD spectra reveal that the secondary structure of eEF1B beta(1-77) consists predominantly of alpha-helices and a portion of disordered region. Very rapid hydrogen/deuterium exchange for all eEF1B beta(1-77) peptides favors a flexible tertiary organization of eEF1B beta(1-77). Computational modeling of eEF1B beta(1-77) suggests several conformation states each composed of three alpha-helices connected by flexible linkers. Altogether, the data imply that the protein-binding domain of eEF1B beta shows flexible spatial organization which may be needed for interaction with eEF1B gamma or other protein partners. (C) 2018 Elsevier B.V. All rights reserved.