Heat Shock Protein 70 (Hsp70) is a molecular chaperone having a major role in protein quality control under normal and stressful conditions. It prevents the aggregation, helps substrate protein folding, protein degradation, transportation, and regulation. Hsp70 has two domains; substrate binding domain (SBD) and nucleotide binding domain (NBD). NBD binds to ATP and performs ATP hydrolysis in order to fold substrate proteins to their native structure. Native structure helps substrate protein to properly function. SBD contains hydrophobic amino acid residues, and this hydrophobic cavity helps unfolded substrate proteins to fold their native structure. Thus, exposed part of the folded proteins may not interact with each other and cause aggregation. The biological activity of Hsp70 family is based on ATP hydrolysis and hydrolysis rate is changed by some of the associated cochaperone proteins.
Cancer cells are exposed to internal and external stress by cytokine attack, hypoxia due to inadequate blood supply, increased free radicals in the cellular milieu as a result, misfolded proteins accumulate in the cell. HSPs play an especially important role in tumor formation and development. Cancer cells gain characteristic features as unlimited division ability, changing their local environment, and spreading to near and far tissues.