Crystallographic structure of the amino terminal domain of yeast initiation factor 4A, a representative DEAD-box RNA helicase

The eukaryotic translation initiation factor 4A (elF4A) is a representative of the DEAD-box RNA helicase protein family. We have solved the crystallog raphic structure of the amino-terminal domain (residues 1-223) of yeast elF 4A. The domain is built around a core scaffold, a parallel alpha-beta motif with five beta strands, that is found in other RNA and DNA helicases, as w ell as in the RecA protein. The amino acid sequence motifs that are conserv ed within the helicase family are localized to the beta strand --> alpha he lix junctions within the core. The core of the amino terminal domain of elF 4A is amplified with additional structural elements that differ from those of other helicases. The phosphate binding loop (the Walker A motif) is in a n unusual closed conformation. The crystallographic structure reveals speci fic interactions between amino acid residues of the phosphate binding loop, the DEAD motif, and the SAT motif, whose alteration is known to impair cou pling between the ATPase cycle and the RNA unwinding activity of elF4A.