Induction and intracellular localization of the 80-kilodalton heat-shock protein of Neurospora crassa.

The most abundant heat-shock protein of Neurospora crassa is a multimeric glycoprotein of 80-kilodaltons (i.e., HSP80), induced strongly by hyperthermia and at a lower level by sodium arsenite, ethanol, and carbon source depletion. Immunoelectron microscopy, using indirect immunogold labelling demonstrated that HSP80 was undetectable in mycelium cultured at the normal growth temperature of 28 degrees C, but it appeared rapidly following the commencement of heat-shock treatment at 48 degrees C. HSP80, visualized by the gold label, was observed almost exclusively in the cytoplasm, exhibiting a uniform distribution. Association of this protein with cellular membranes and (or) targeting to a particular subcellular compartment or organelle was not apparent.