A 75 kDa glucose regulated protein (GRP75) is a mitochondrial matrix protein that is generally recognized as a member of the heat shock protein 70 (HSP70) class of proteins. GRP75 is induced under conditions of low glucose and other nutritional and environmental stresses. Closely related proteins have been identified in the immune system (PBP74; CSA), liver (mtHSP70), and cell lines. GRP75 is involved in various chaperoning functions in protein translocation, folding, and function in mitochondria. It also appears to be involved in antigen recognition, cell proliferation, and senescence. Although primarily localized in mitochondria, related forms may be found in cytosol or on the surface of the extracellular membrane.This polyclonal antibody is specific for a peptide corresponding to an amino terminal fragment of human GRP75, and has been successfully used for immunoprecipitation, Western blotting, and immunohistochemical detection of GRP75 in human and murine cells. It recognizes both precursor and mature GRP75, and should be useful for studying the chaperoning and stressor responsive functions of GRP75. It does not cross-react with other members of the HSP70 family.