title: The DnaK chaperones from the archaeon Methanosarcina mazei and the bacterium Escherichia coli have different substrate specificities.
abstract: Hsp70 (DnaK) is a highly conserved molecular chaperone present in bacteria, eukaryotes, and some archaea. In a previous work we demonstrated that DnaK from the archaeon Methanosarcina mazei (DnaK(Mm)) and the DnaK from the bacterium Escherichia coli (DnaK(Ec)) were functionally similar when assayed in vitro but DnaK(Mm) failed to substitute for DnaK(Ec) in vivo. Searching for the molecular basis of the observed DnaK species specificity we compared substrate binding by DnaK(Mm) and DnaK(Ec). DnaK(Mm) showed a lower affinity for the model peptide (a-CALLQSRLLS) compared to DnaK(Ec). Furthermore, it was unable to negatively regulate the E. coli sigma32 transcription factor level under heat shock conditions and poorly bound purified sigma32, which is a native substrate of DnaK(Ec). These observations taken together indicate differences in substrate specificity of archaeal and bacterial DnaKs. Structural modeling of DnaK(Mm) showed some structural differences in the substrate-binding domains of DnaK(Mm) and DnaK(Ec), which may be responsible, at least partially, for the differences in peptide binding. Size-exclusion chromatography and native gel electrophoresis revealed that DnaK(Mm) was found preferably in high molecular mass oligomeric forms, contrary to DnaK(Ec). Oligomers of DnaK(Mm) could be dissociated in the presence of ATP and a substrate (peptide) but not ADP, which may suggest that monomer is the active form of DnaK(Mm).
authors: Department of Biochemistry, University of Gdańsk, Gdańsk, Poland.
authors: Michal A
authors: MA
authors: Zmijewski
authors: Joanna
authors: J
authors: Skórko-Glonek
authors: Fabio
authors: F
authors: Tanfani
authors: Bogdan
authors: B
authors: Banecki
authors: Agnieszka
authors: A
authors: Kotlarz
authors: Alberto J L
authors: AJ
authors: Macario
authors: Barbara
authors: B
authors: Lipińska
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D019843:Archaeal Proteins / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D002850:Chromatography, Gel; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D006360:Heat-Shock Proteins; D015151:Immunoblotting; D017020:Methanosarcina / Q000378:metabolism*; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D012808:Sigma Factor / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared; D013379:Substrate Specificity
chemical_list: D019843:Archaeal Proteins; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D010455:Peptides; D012808:Sigma Factor; C069774:heat-shock sigma factor 32; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate