Hsp27 exhibits a chaperone-like activity by serving as a site where unfolding proteins may bind until ATP and Hsp70-dependent refolding can occur. Hsp27 is believed to protect cells by enhancing cellular glutathione levels and elevated glutathione levels have been measured in cells overexpressing Hsp27. Data from studies using wild-type Hsp27 and mutant forms in which the serine phosphorylation sites were mutated to alanines, glycines or aspartates, have shown that cellular glutathione levels depend on the oligomerization of Hsp27. Recent findings indicate that Hsp27 is also a negative regulator of cytochrome c-dependent activation of procaspase-3.