Abstract:

<p>Protein synthesis is a key process in all living organisms. In eukaryotes, Initiation Factor 2 (eIF2) plays an important role in translation initiation as it selects and delivers the initiator tRNA to the small ribosomal subunit. Under stress conditions, phosphorylation of the α-subunit of eIF2 downregulates cellular protein synthesis. However, translation of certain mRNAs continues via the eIF2D dependent non-canonical initiation pathway. The molecular mechanism of this process remains elusive. In addition, eIF2D plays a role in translation re-initiation and ribosome recycling. Currently, there has been no structural information of eIF2D. We have now determined the crystal structure of the C-terminal domains of eIF2D at 1.4Å resolution. One domain has the fold similar to that of eIF1, which is crucial for the scanning and initiation codon selection. The second domain has a known SWIB/MDM2 fold, which was not observed before in other translation initiation factors. Our structure reveals atomic details of inter-domain interactions in the C-terminal part of eIF2D and sheds light on the possible role of these domains in eIF2D during translation.</p>