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

Abstract

The eukaryotic translation initiation factor 4A (eIF4A) is a representative of the DEAD-box RNA helicase protein family. We have solved the crystallographic structure of the amino-terminal domain (residues 1–223) of yeast eIF4A. The domain is built around a core scaffold, a parallel α–β motif with five β strands, that is found in other RNA and DNA helicases, as well as in the RecA protein. The amino acid sequence motifs that are conserved within the helicase family are localized to the β strand →→→→ α helix junctions within the core. The core of the amino terminal domain of eIF4A is amplified with additional structural elements that differ from those of other helicases. The phosphate binding loop (the Walker A motif) is in an unusual closed conformation. The crystallographic structure reveals specific interactions between amino acid residues of the phosphate binding loop, the DEAD motif, and the SAT motif, whose alteration is known to impair coupling between the ATPase cycle and the RNA unwinding activity of eIF4A.