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.