Co-chaperone that regulates diverse cellular pathways, such as programmed cell death and stress responses. Necessary for the proper maintenance of the unfolded protein response (UPR) during heat and cold tolerance. Binds to the ATPase domain of HSP70/HSC70 chaperones (By similarity). Interacts with HSP70-11/BIP2. IQ domain mediates interaction with calmodulin. Susceptibility to heat and cold stress.