Chaperone that expresses an ATPase activity. Localizes to the cortical actin cytoskeleton. Translocates to the mitochondrion during the prestarvation response and in response to differentiation. In prespore cells, colocalizes with grp94 in the prespore-specific vacuole. Found in the outermost layer of spore cell wall. Defects in prestarvation response, sporulation and in resistance to heat shock. When overexpressed, induces precocious aggregation, however, development arrests before the tight mound stage. Belongs to the heat shock protein 90 family.