Protein Domain : Activator of Hsp90 ATPase AHSA1-like, N-terminal IPR015310

Type	Domain
Description	This entry includes a group of heat shock protein interacting proteins, including AHSA1/2 from animals and Aha1/Hch1 from budding yeasts, and it represents a domain found at the N-terminal of Aha1 and AHSA1/2, while in Hch1 is the only domain. Aha1 adopts a secondary structure consisting of an N-terminal α-helix leading into a four-stranded meandering antiparallel β-sheet, followed by a C-terminal α-helix. The two α-helices are packed together, with the β-sheet curving around them. The N-terminal domain of Aha1 interacts with the central segment of Hsp90 which induces the conformational rearrangements of Hsp90 that favor the N-terminal domain-dimerized state of the chaperone and ends leads to the stimulation of its ATPase activity []. Activator of 90kDa heat shock protein ATPase Aha1/AHSA1 (AHSA1/p38, ) is known to interact with the middle domain of Hsp90, and stimulate its ATPase activity [ , ], where one Aha1/AHSA1 molecule per Hsp90 dimer is sufficient for this stimulation. It is probably a general up regulator of Hsp90 function, particularly contributing to its efficiency in conditions of increased stress []. It is also known to interact with the cytoplasmic domain of the VSV G protein, and may thus be involved in protein transport []. It has also been reported as being under expressed in Down's syndrome.In budding yeasts, both Hch1 and Aha1 bind to the middle domain of Hsp90 and stimulate ATPase activity [ , ]. However, Aha1 but not Hch1 stimulated the intrinsic ATPase activity of Hsp90 5-fold []. Hch1 and Aha1 may regulate Hsp90 function in distinct ways [].
Short Name	AHSA1-like_N