1l8b
From Proteopedia
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Cocrystal Structure of the Messenger RNA 5' Cap-binding Protein (eIF4E) bound to 7-methylGpppG
Overview
mRNA 5'-cap recognition by the eukaryotic translation initiation factor, eIF4E has been exhaustively characterized with the aid of a novel, fluorometric, time-synchronized titration method, and X-ray, crystallography. The association constant values of recombinant eIF4E for, 20 different cap analogues cover six orders of magnitude; with the highest, affinity observed for m(7)GTP (approximately 1.1 x 10(8) M(-1)). The, affinity of the cap analogues for eIF4E correlates with their ability to, inhibit in vitro translation. The association constants yield, contributions of non-covalent interactions involving single structural, elements of the cap to the free energy of binding, giving a reliable, starting point to rational drug design. The free energy of 7-methylguanine, stacking and hydrogen bonding (-4.9 kcal/mol) is separate from the, energies of phosphate chain interactions (-3.0, -1.9, -0.9 kcal/mol for, alpha, beta, gamma phosphates, respectively), supporting two-step, mechanism of the binding. The negatively charged phosphate groups of the, cap act as a molecular anchor, enabling further formation of the, intermolecular contacts within the cap-binding slot. Stabilization of the, stacked Trp102/m(7)G/Trp56 configuration is a precondition to form three, hydrogen bonds with Glu103 and Trp102. Electrostatically steered eIF4E-cap, association is accompanied by additional hydration of the complex by, approximately 65 water molecules, and by ionic equilibria shift., Temperature dependence reveals the enthalpy-driven and entropy-opposed, character of the m(7)GTP-eIF4E binding, which results from dominant, charge-related interactions (DeltaH degrees =-17.8 kcal/mol, DeltaS, degrees= -23.6 cal/mol K). For recruitment of synthetic eIF4GI, eIF4GII, and 4E-BP1 peptides to eIF4E, all the association constants were, approximately 10(7) M(-1), in decreasing order: eIF4GI>4E-BP1>eIF4GII, approximately 4E-BP1(P-Ser65) approximately 4E-BP1(P-Ser65/Thr70)., Phosphorylation of 4E-BP1 at Ser65 and Thr70 is insufficient to prevent, binding to eIF4E. Enhancement of the eIF4E affinity for cap occurs after, binding to eIF4G peptides.
About this Structure
1L8B is a Single protein structure of sequence from Mus musculus with MGP as ligand. Full crystallographic information is available from OCA.
Reference
Biophysical studies of eIF4E cap-binding protein: recognition of mRNA 5' cap structure and synthetic fragments of eIF4G and 4E-BP1 proteins., Niedzwiecka A, Marcotrigiano J, Stepinski J, Jankowska-Anyszka M, Wyslouch-Cieszynska A, Dadlez M, Gingras AC, Mak P, Darzynkiewicz E, Sonenberg N, Burley SK, Stolarski R, J Mol Biol. 2002 Jun 7;319(3):615-35. PMID:12054859
Page seeded by OCA on Tue Nov 20 20:22:17 2007
