May play a role in late differentiation as well as in starvation response. When overexpressed, suppresses the ability to form normal fruiting bodies and impairs prespore differentiation as well as maturation into spores. In prespore cells, preferentially localizes in Golgi vesicles and cisternae. Colocalizes with trap1 in the prespore-specific vacuole. Expression is greatly reduced following starvation. Phosphorylated. Belongs to the heat shock protein 90 family.