Acts as a chaperone. Recombinant extracellular protein activates expression of NF-kappa-B in immortalized human dermal endothelial cells in a TLR2- and TLR4-dependent manner. Activation occurs via MYD88-dependent and -independent pathways and requires TIRAP, TRIF and TRAM (some experiments done in mouse cells, mice do not usually catch tuberculosis) (PubMed:15809303). Although thought of as a cytoplasmic chaperone this protein is routinely found extracellularly in the absence of cell lysis (PubMed:19470749). Present in extracytoplasmic vesicles (PubMed:21364279). By stress conditions e.g. heat shock and oxidative stress under control of SigH. There is another promoter. Belongs to the heat shock protein 70 family.