Chaperone required for protein translocation and folding in the endoplasmic reticulum. ATP + H2O = ADP + H(+) + phosphate Interacts with the heat shock protein 70 (HSP70) KAR2, and this stimulates nucleotide exchange on KAR2. KAR2 in turn acts to stimulate the ATPase activity of LHS1. By the unfolded protein response (UPR). N-glycosylated. Present with 137 molecules/cell in log phase SD medium. Belongs to the heat shock protein 70 family.