DEAD-box helicases catalyze the ATP-dependent unwinding of RNA duplexes. They 
share a helicase core formed by two RecA-like domains that carries a set of 
conserved motifs contributing to ATP binding and hydrolysis, RNA binding and 
duplex unwinding. The translation initiation factor eIF4A is the founding member 
of the DEAD-box protein family, and one of the few examples of DEAD-box proteins 
that consist of a helicase core only. It is an RNA-stimulated ATPase and a 
non-processive helicase that unwinds short RNA duplexes. In the catalytic cycle, 
a series of conformational changes couples the nucleotide cycle to RNA 
unwinding. eIF4A has been considered a paradigm for DEAD-box proteins, and 
studies of its function have revealed the governing principles underlying the 
DEAD-box helicase mechanism. However, as an isolated helicase core, eIF4A is 
rather the exception, not the rule. Most helicase modules in other DEAD-box 
proteins are modified, some by insertions into the RecA-like domains, and the 
majority by N- and C-terminal appendages. While the basic catalytic function 
resides within the helicase core, its modulation by insertions, additional 
domains or a network of interaction partners generates the diversity of DEAD-box 
protein functions in the cell. This review summarizes the current knowledge on 
eIF4A and its regulation, and discusses to what extent eIF4A serves as a model 
DEAD-box protein.