This domain is predominantly found N-terminal in the protein Activator of Hsp90 ATPase (Aha1). Aha1 adopts a secondary structure consisting of an N-terminal alpha-helix leading into a four-stranded meandering antiparallel beta-sheet, followed by a C-terminal alpha-helix. The two alpha helices are packed together, with the beta-sheet curving around them. The N-terminal domain of Aha1 interacts with Hsp90 and stimulates its ATPase activity.