Abstract
The X-ray structure of the eukaryotic translation initiation factor 4E (eIF4E), bound to 7-methyl-GDP, has been determined at 2.2 Å resolution. eIF4E recognizes 5′ 7-methyl-G(5′)ppp(5′)N mRNA caps during the rate-limiting initiation step of translation. The protein resembles a cupped hand and consists of a curved, 8-stranded antiparallel β sheet, backed by three long α helices. 7-methyl-GDP binds in a narrow cap-binding slot on the molecule's concave surface, where 7-methyl-guanine recognition is mediated by base sandwiching between two conserved tryptophans, plus formation of three hydrogen bonds and a van der Waals contact between its N7-methyl group and a third conserved tryptophan. The convex dorsal surface of the molecule displays a phylogenetically conserved hydrophobic/acidic portion, which may interact with other translation initiation factors and regulatory proteins.