The binding mechanism of eIF2β with its partner proteins, eIF5 and eIF2Bε.
The eukaryotic translation initiation factor eIF2 delivers Met-tRNAiMet to the ribosomal small subunit in GTP-bound form associated with eIF1, eIF1A, eIF3 and eIF5, and dissociates together with eIF5 as eIF5-eIF2-GDP complex from the ribosomal small subunit after formation of start codon-anticodon base pairing between Met-tRNAiMet and mRNA. The inactive form eIF2-GDP is then exchanged for the active form eIF2-GTP by eIF2B for further initiation cycle. Previous studies showed that the C-terminal domains of eIF5 (eIF5-CTD) and eIF2Bε (eIF2Bε-CTD) have a common eIF2β-binding site for interacting with an N-terminal region of eIF2β (eIF2β-NTD). Here we have reconstructed the complexes of (eIF5-CTD)-(eIF2β-NTD) and (eIF2Bε-CTD)-(eIF2β-NTD) in vitro, and investigated binding mechanism by circular dichroism spectroscopy and small angle X-ray scattering in solution. The results showed the conformation of eIF2β-NTD was changed when bound to partner proteins, whereas the structures of eIF5-CTD and eIF2Bε-CTD were similar in both isolated and complex states. We propose that eIF2β-NTD works as an intrinsically disordered domain which is disorder in the isolated state, but folds into a definite structure when bound to its partner proteins. Such flexibility of eIF2β-NTD is expected to be responsible for its binding capability.
Graduate School of Life Science, Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810, Japan.
Zuoqi
Z
Gai
Yumie
Y
Kitagawa
Yoshikazu
Y
Tanaka
Nobutaka
N
Shimizu
Keisuke
K
Komoda
Isao
I
Tanaka
Min
M
Yao
D002942:Circular Dichroism; D020717:Eukaryotic Initiation Factor-2B / Q000737:chemistry*; D008956:Models, Chemical; D010448:Peptide Initiation Factors / Q000737:chemistry*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000737:chemistry*; D012441:Saccharomyces cerevisiae; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction; D000097574:Eukaryotic Translation Initiation Factor 5A
D020717:Eukaryotic Initiation Factor-2B; D010448:Peptide Initiation Factors; D016601:RNA-Binding Proteins; D000097574:Eukaryotic Translation Initiation Factor 5A