The largest group of RNA remodeling proteins in the cell are the DEAD subgroup (so-named after the amino acid sequence in conserved motif II of SF2 proteins). Unlike NS3 and NPH-II, these proteins do not move directionally on RNA but they undergo ATP-dependent conformational changes that reorganize the conformation of large RNA molecules and ribonucleoprotein complexes. They are also strong, ATP-regulated RNA binding proteins that assist in the assembly of large RNA machines. DEAD proteins are essential for pre-mRNA splicing, translation initiation, RNA export and most other aspects of RNA metabolism. We are studying the role of DEAD proteins in tertiary structure formation by focusing on the yeast protein Mss116, which stimulates self-splicing of group I and group II introns in vivo and in vitro (Huang et al, PNAS 2005; Solem et al, Molec Cell 2006) . Mss116-stimulated splicing by group II introns is a particularly useful model system for examining the role of motor proteins in RNA tertiary folding because the biologically relevant reaction can be recapitulated from purified components and studied in a test tube (Pyle, Annu Rev Biophys 2008).