Domain-dependent Interaction of Eukaryotic Initiation Factor eIF4A for Binding to Middle and C-terminal Domains of eIF4G
The Journal of Biochemistry,
2009, 146(3), 359-368. DOI: 10.1093/jb/mvp078
The interactions of recombinant human eIF4A (4A) and its N- and C-terminal side domains (AN and AC, respectively) with the middle- and C-terminal-domain-linked fragment (GMC) of eIF4G and its middle and C-terminal domains (GM and GC, respectively) were investigated by surface plasmon resonance (SPR) analysis and isothermal titration calorimetry (ITC). It is remarkable that the kinetic parameter-dependent SPR profile observed for the 4A–GMC pair was quite different from the steady affinity profiles of the 4A–GM/GC pairs, suggesting the simultaneous contribution of the middle and C-terminal domains of eIF4G for the binding with eIF4A. On the other hand, ITC yielded the enthalpy energies of –1.5 x 104 to –2.5 x 104 J/mol for the domain–domain interactions of 4A with GMC. Although the ITC profile of the 4A–GM pair reflects well the structural feature shown previously by NMR and X-ray analyses, it was essentially different from that of the 4A-GMC pair. The present results suggest that the intimate interaction between the eIF4A N- and C-terminal domains and the eIF4G middle and C-terminal domains is necessary to reveal the biologically active function of the eIF4A–eIF4G complex.