Selective Pharmacological Targeting of a DEAD Box RNA Helicase
Figure 1
Hippuristanol binds to eIF4AI-CTD.
(A) Chemical shift changes of 1H-15N-HSQC peaks, (Δδ(1H)+0.2 Δδ(15N), of eIF4A-I-CTD (52 µM) upon addition of hippuristanol (100 µM). Free and bound forms are in slow exchange and the resonances of eIF4AI-CTD had to be assigned in both states. The locations of secondary structures were identified by NMR and are indicated with magenta arrows (β-strands) and yellow rectangles (helices). (B) Primary amino acid sequence of eIF4AI indicating residues involved in hippuristanol binding. NOEs are highlighted in yellow, whereas those within 5Å are in grey and correspond to regions a, b, and c in A. Residues in bold denote conserved amino acids that define motifs V (ARGID) and VI (HRIGRGGRFG) of DEAD box family members [40]. Arrows denote residues identified in Vasa that interact with ATP (red), RNA (blue), or are involved in interdomain interaction (green)[25]. (C) Surface and ribbon representations of the model for eIF4AI-CTD. The CTD is viewed from the position of the NTD. Residues of eIF4AI-CTD that show NOEs to hippuristanol are coloured yellow, those exhibiting major chemical shift changes but no NOEs are coloured blue. Residues contacting eIF4G are in red [24]. The β-sheets (E1–E6) and α-helices (H1–H6) are labelled and refer to the locations marked in A. RNA and ADPNP are shown as sticks models. (D) Location of the hippuristanol-binding site in a model for eIF4AI complexed with RNA and ADPNP. The model is composed of the crystal structure of human eIF4AI-NTD (PDB #2G9N) and the homology model of the eIF4AI-CTD [24]. The two domains are aligned to the structure of eIF4AIII from the EJC from which the RNA and ADPNP binding sites are adapted (PDB# 2HYI) [22]. Color scheme of amino acid residues is as in C.