Stress induced phosphoprotein 1(STIP1) Homo sapiens STIP1 is an adaptor protein that coordinates the functions of HSP70 (see HSPA1A; MIM 140550) and HSP90 (see HSP90AA1; MIM 140571) in protein folding. It is thought to assist in the transfer of proteins from HSP70 to HSP90 by binding both HSP90 and substrate-bound HSP70. STIP1 also stimulates the ATPase activity of HSP70 and inhibits the ATPase activity of HSP90, suggesting that it regulates both the conformations and ATPase cycles of these chaperones.