ATPase Site Architecture Is Required for Self-Assembly and Remodeling Activity of a Hexameric AAA+ Transcriptional Activator

AAA+ proteins (ATPases associated with various cellular activities) are oligomeric ATPases that use ATP hydrolysis to remodel their substrates. By similarity with GTPases, a dynamic organization of the nucleotide-binding pockets between ATPase protomers is proposed to regulate functionality. Using the transcription activator PspF as an AAA+ model, we investigated contributions of conserved residues for roles in ATP hydrolysis and intersubunit communication. We determined the R-finger residue and revealed that it resides in a conserved " R-hand" motif (R _xD _xxxR) needed for its " trans-acting" activity. Further, a divergent Walker A glutamic acid residue acts synergistically with a tyrosine residue to function in ADP-dependent subunit-subunit coordination, forming the " ADP-switch" motif. Another glutamic acid controls hexamer formation in the presence of nucleotides. Together, these results lead to a " residue-nucleotide" interaction map upon which to base AAA+ core regulation.