Heat shock proteins (HSPs) were originally described in the early 1960s by the pioneering work of Ferruccio Ritossa on the fruit fly Drosophila melanogaster 5,6,7. Expression of HSPs was found as being induced after exposure to different kinds of stress such as heat shock and could be demonstrated subsequently in any cellular organism 8. Nevertheless, other stress conditions, including heavy metals, hypoxia, nutrient deprivation and irradiation as well as oxidative and toxic stress, infections and exposure to inflammatory cytokines are also able to induce HSP expression 8, 9. Members of the HSP70 family were identified for the first time as being upregulated in bacteria in response to cellular stress 10. The painstaking analysis of the limited number of proteins firstly identified by heat shock induction in D. melanogaster and in E. coli led to the finding that DnaK, DnaJ and GrpE were also members of the heat shock class of proteins. In 1984, Bardwell and Craig demonstrated that the E. coli DnaK and the Drosophila 70 kDa heat shock proteins were highly conserved at the sequence level 11. Moreover, hybridization between the DNA of the archaebacterium Methanosarcina barkeri and the HSP70 genes of D. melanogaster, Saccharomyces cerevisiae, and E. coli has been detected, suggesting the existence of Hsp70-related genes in the three “primary kingdoms”: eukaryotes, eubacteria, and archaebacteria11.
The HSP70 Family
The HSP70 family represents the most conserved and best characterized group of HSPs comprising polypeptides whose molecular weights range from 66 – 78 kDa and that are encoded by a multigene family encompassing up to 17 genes and 30 pseudogenes in humans 19. Functional genes encoding HSP70 proteins map to human chromosomes 6, 14, 21, and at least one other chromosome 20. The most studied genes are HSPA1A and HSPA1B encoding proteins that only differ by two amino acids and are believed as being completely interchangeable proteins. The genes are clustered in the major histocompatibility complex class III region on chromosome 6p21.3.The HSP70 family constitutes one of the most conserved protein families in evolution. Their members are present in all organisms and subcellular compartments and can be found from archaebacteria and plants to humans. In archaea and eubacteria Hsp70 is referred to as DnaK. In yeasts they are called Ssa, in mammals including humans they are referred to as HspA.
More information is available on the HSP70 website
and antibodies and related products are available by searching on the Newmarket Scientific website.
References:
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6. Ritossa,F. New puffs induced by temperature shock, DNP and salicilate in salivary chromosomes of D. melanogaster. Drosophila Information Service37, 122-123 (1963). [Drosophila Information Service]
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11. Bardwell,J.C. & Craig,E.A. Major heat shock gene of Drosophila and the Escherichia coli heat-inducible dnaK gene are homologous. Proc. Natl. Acad. Sci. U. S. A81, 848-852 (1984). [PubMed]
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20. Harrison,G.S. et al. Chromosomal location of human genes encoding major heat-shock protein HSP70. Somat. Cell Mol. Genet.13, 119-130 (1987). [PubMed]
