The Hsp60 of Heliothis viescens is a member of a highly conserved
family which includes molecular chaperones from several species
such as plant Hsp60 (known as Rubisco binding protein), GroEL,
the E.coli Hsp60 and 65 kDa major antigen of mycobacteria. In eukaryotes,
Hsp60 is localized in the mitochondrial matrix and in plants Hsp60
is localized in the chloroplast. Mitochondria, chloroplasts and
bacteria have a common ancestry (>1billion years) and this fact
together with the high degree of homology between the divegent
Hsp60s would indicate that these proteins carry out a primitive
but important function which is similar to all of these different
species. The common characteristics of the Hsp60s from the divergent
species are i) high abundance, ii) induction with environmental
stress such as heat shock, iii) homo-oligomeric structures of either
7 or 14 subunits which reversibly dissociate in the presence of
Mg2+ and ATP, iv) ATPase activity and v) a role in folding and
assembly of oligomeric protein structures. These similarities are
supported by recent studies where the single-ring human mitochondrial
homolog, Hsp60 with its co-chaperonin, Hsp10 were expressed in
a E. coli strain, engineered so that the groE operon is under strict
regulatory control. This study has demonstrated that expression
of Hsp60-Hsp10 was able to carry out all essential in vivo functions
of GroEL and its co-chaperonin, GroES. Consistent with their functions
as chaperones, Hsp60 and Hsp10 have been suggested to act as docking
molecules with a passive role in the maturation of caspase processing.
Data demonstrates that recombinant Hsp60 and Hsp10 have been shown
to accelerate the activation of procaspase-3 by cytochrome c and
dATP in an ATP-dependent manner. Hsps are intracellular proteins
which are thought to serve protective functions against infection
and cellular stress, however several recent studies indicate that
members of the Hsp60 family are linked to a number of autoimmune
diseases, artherosclerosis and chlamydial disease.
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