Archaebacterial heat-shock proteins.

The response to heat shock was examined in seven archaebacterial strains from the genus Halobacterium. Upon heat shock each strain preferentially synthesized a limited number of proteins which fell into three narrow mol. wt. ranges. Further examination of the heat-shock response in H. volcanii revealed that heat-shock protein (hsp) synthesis was greatest at 60 degrees C. Synthesis of hsps at this induction temperature was both rapid and transient. Cells recovered their normal protein synthesis patterns rapidly upon returning to their normal growth temperature following heat shock. H. volcanii cells also responded with a ;heat shock-like' response to salt dilution, a natural environmental stress for these organisms. These results indicate that the heat shock or stress response which is charactertistic of eukaryotic and eubacterial cells is also present among members of the archaebacterial genus Halobacterium.