DEAD-box proteins are ubiquitous in RNA-mediated processes and function by 
coupling cycles of ATP binding and hydrolysis to changes in affinity for 
single-stranded RNA. Many DEAD-box proteins use this basic mechanism as the 
foundation for a version of RNA helicase activity, efficiently separating the 
strands of short RNA duplexes in a process that involves little or no 
translocation. This activity, coupled with mechanisms to direct different 
DEAD-box proteins to their physiological substrates, allows them to promote RNA 
folding steps and rearrangements and to accelerate remodeling of RNA–protein 
complexes. This review will describe the properties of DEAD-box proteins as RNA 
helicases and the current understanding of how the energy from ATPase activity 
is used to drive the separation of RNA duplex strands. It will then describe how 
the basic biochemical properties allow some DEAD-box proteins to function as 
chaperones by promoting RNA folding reactions, with a focus on the self-splicing 
group I and group II intron RNAs.