Delayed Discovery of Hsp60 and Subsequent Characterization of Moonlighting Functions of Multiple Genes in : a Personal Historical Perspective

The pioneering studies carried out on heat shock-induced synthesis of specific proteins in the early 1970s did not identify any Hsp60 family protein in . By the early 1980s, although the members of Hsp60 family of heat shock proteins (Hsp) were identified in a wide range of eukaryotes as homologs of the bacterial GroEL, none was known in . The existence of the Hsp60 family protein was serendipitously revealed in in my laboratory in 1989. Contrary to the earlier reports that all tissues in flies display the canonical heat shock response, the larval Malpighian tubules (MT) did not show induction of any of the major Hsps but synthesis of a putative Hsp60 family protein was found to be the most abundant in this tissue. A few years later, we identified this MTspecific heat shock-induced protein to indeed be a member of the Hsp60/chaperonin family. The genome sequence projects subsequently revealed four putative gene sequences in the . genome. The present historical perspective chronicles contributions from my and other laboratories that unraveled several aspects of intriguing biology of the multiple genes in . , and highlights challenging questions awaiting future studies.