A spectroscopic study of the binding of m7GTP and m7GpppG to human protein synthesis initiation factor 4E.
The binding of analogues of the 7-methylguanosine-containing cap, m7GTP and m7GpppG, to eIF-4E from human erythrocytes as a function of pH, temperature, and ionic strength is described. From the pH-dependent binding of m7GTP and m7GpppG to eIF-4E, a new model describing the nature of the cap.eIF-4E interaction is proposed. The thermodynamic values and ionic strength dependence of binding are consistent with a binding site which is primarily hydrophobic. Fluorescence and circular dichroism data indicate that tryptophan residues may be involved in base-stacking interactions with the cap in a somewhat buried environment. The model presented here confirms the earlier proposal [Rhoads et al. (1983) Biochemistry 22, 6084-6088] that the enolate tautomer of the cap is preferred for interaction and further proposes that the interaction is with a protonated amino acid residue, such as histidine, while stacking with an aromatic amino acid, such as tryptophan.
Carberry
S E
SE
Department of Chemistry, Hunter College City University of New York, New York 10021.
Rhoads
R E
RE
Goss
D J
DJ
D002942:Circular Dichroism; D015226:Dinucleoside Phosphates / Q000378:metabolism*; D039561:Eukaryotic Initiation Factor-4E; D006863:Hydrogen-Ion Concentration; D010448:Peptide Initiation Factors / Q000378:metabolism*; D011485:Protein Binding; D012314:RNA Cap Analogs / Q000378:metabolism*; D012315:RNA Caps / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013696:Temperature
D015226:Dinucleoside Phosphates; D039561:Eukaryotic Initiation Factor-4E; D010448:Peptide Initiation Factors; D012314:RNA Cap Analogs; D012315:RNA Caps; D012333:RNA, Messenger; C017516:7-methylguanosine triphosphate; C062229:7-methyl-diguanosine triphosphate