Journal of Biochemistry Advance Access originally published online on July 6, 2006
Journal of Biochemistry 2006 140(2):237-246; doi:10.1093/jb/mvj143
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© 2006 The Japanese Biochemical Society.
Regular Paper |
Effect of N-Terminal Region of eIF4E and Ser65-Phosphorylation of 4E-BP1 on Interaction between eIF4E and 4E-BP1 Fragment Peptide
1 Department of Physical Chemistry, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094; and 2 Research Center, Taisho Pharmaceutical Co., Ltd., 1-403 Yoshino-cho, Kita-ku, Saitama 331-9530
* To whom correspondence should be addressed. Tel/Fax: +81-726-90-1068, E-mail: ishida{at}gly.oups.ac.jp
To clarify the contribution of N-terminal region of eukaryotic initiation factor 4E (eIF4E) to the interaction with 4E-BP and to investigate the effect of 4E-BP phosphorylation on the interaction with eIF4E, the interaction profiles of the Ser65-unphosphorylated and phosphorylated peptides (Thr37Thr70 fragment of 4E-BP1) with full-length and N-terminal 33 residuesdeleted eIF4Es were investigated by fluorescence and SPR methods. The effect of N-terminal region of eIF4E on the interaction with 4E-BP1 peptides was shown to be dependent on the interaction state, that is, the steady-state fluorescence and kinetic-state SRP analyses showed the positive and negative contributions of the N-terminal region to the interaction with the peptide, respectively, despite its unphosphorylated or phosphorylated state. The comparison of the association constants of the peptide with those of full-length 4E-BP1 indicated the importance of N-terminal (136) and/or C-terminal (71118) sequence of 4E-BP1 for the interaction, although the MD simulations suggested that the
-helical region (Arg56Cys62) of 4E-BP1 peptide is sufficient for keeping the interaction. The MD simulations also indicated that a charge-dependent rigid hydration shell formed around the phosphate group makes the molecular conformation rigid, and single Ser65 phosphorylation is insufficient for releasing 4E-PB1 peptide from eIF4E.