title: Functional similarities and differences of an archaeal Hsp70(DnaK) stress protein compared with its homologue from the bacterium Escherichia coli.
abstract: Archaea are prokaryotes but some of their chaperoning systems resemble those of eukaryotes. Also, not all archaea possess the stress protein Hsp70(DnaK), in contrast with bacteria and eukaryotes, which possess it without any known exception. Further, the primary structure of the archaeal DnaK resembles more the bacterial than the eukaryotic homologues. The work reported here addresses two questions: Is the archaeal Hsp70 protein a chaperone, like its homologues in the other two phylogenetic domains? And, if so, is the chaperoning mechanism of bacterial or eukaryotic type? The data have shown that the DnaK protein of the archaeon Methanosarcina mazei functions efficiently as a chaperone in luciferase renaturation in vitro, and that it requires DnaJ, and the other bacterial-type chaperone, GrpE, to perform its function. The M. mazei DnaK chaperone activity was enhanced by interaction with the bacterial co-chaperone DnaJ, but not by the eukaryotic homologue HDJ-2. Both the bacterial GrpE and DnaJ stimulated the ATPase activity of the M. mazei DnaK. The M. mazei DnaK-dependent chaperoning pathway in vitro is similar to that of the bacterium Escherichia coli used for comparison. However, in vivo analyses indicate that there are also significant differences. The M. mazei dnaJ and grpE genes rescued E.coli mutants lacking these genes, but E.coli dnaK mutants were not complemented by the M. mazei dnaK gene. Thus, while the data from in vitro tests demonstrate functional similarities between the M. mazei and E.coli DnaK proteins, in vivo results indicate that, intracellularly, the chaperones from the two species differ.
authors.affiliation: Department of Biochemistry, University of Gdańsk, Klz.shtsls;adki 24, 80-822, Gdańsk, Poland.
authors.forename: Michał A
authors.initials: MA
authors.lastname: Zmijewski
authors.forename: Alberto J L
authors.initials: AJ
authors.lastname: Macario
authors.forename: Barbara
authors.initials: B
authors.lastname: Lipińska
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005816:Genetic Complementation Test; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D017020:Methanosarcina / Q000201:enzymology* / Q000235:genetics; D017510:Protein Folding; D020673:Protein Renaturation; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D019843:Archaeal Proteins; D001426:Bacterial Proteins; C494635:DnaJ protein, E coli; D029968:Escherichia coli Proteins; C068113:GrpE protein, Bacteria; C489400:GrpE protein, E coli; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D011994:Recombinant Proteins; D008156:Luciferases; D000251:Adenosine Triphosphatases; C063842:dnaK protein, E coli