Kinetics and Thermodynamics of the ATPase Cycle of the DEAD-Box Protein Dbp5

DEAD-box proteins are ubiquitous ATPase motor proteins involved in all aspects of RNA metabolism including folding, duplex unwinding and ribonucleoprotein remodeling. Although all characterized DEAD-box proteins share a similar ATPase cycle, differences in individual ATP utilization rate and equilibrium constants confer unique motor properties for carrying out physiological functions, analogous to cytoskeletal motors (i.e. myosin, kinesin, dynein). RNA helicase functional diversity is therefore contained in their ATPase cycles, and versatility introduced through interactions with regulatory partners. Dbp5 is a yeast DEAD-box protein that, in conjunction with several regulatory proteins and small molecules, plays an essential role in mRNA export from the nucleus to cytosol. We present a kinetic and equilibrium analysis of the Dbp5 ATPase as context for studying the role of the regulatory partners.