The N-terminal domain of Escherichia coli ClpB enhances chaperone function.
ClpB/Hsp104 collaborates with the Hsp70 system to promote the solubilization and reactivation of proteins that misfold and aggregate following heat shock. In Escherichia coli and other eubacteria, two ClpB isoforms (ClpB95 and ClpB80) that differ by the presence or absence of a highly mobile 149-residues long N-terminus domain are synthesized from the same transcript. Whether and how the N-domain contributes to ClpB chaperone activity remains controversial. Here, we show that, whereas fusion of a 20-residues long hexahistidine extension to the N-terminus of ClpB95 interferes with its in vivo and in vitro activity, the same tag has no detectable effect on ClpB80 function. In addition, ClpB95 is more effective than ClpB80 at restoring the folding of the model protein preS2-beta-galactosidase as stress severity increases, and is superior to ClpB80 in improving the high temperature growth and low temperature recovery of dnaK756 DeltaclpB cells. Our results are consistent with a model in which the N-domain of ClpB95 maximizes substrate processing under conditions where the cellular supply of free DnaK-DnaJ is limiting.
Chow
I-Ting
IT
Department of Chemical Engineering, University of Washington, Box 351750, Seattle, WA 98195, USA.
Barnett
Micheal E
ME
Zolkiewski
Michal
M
Baneyx
François
F
D049071:Endopeptidase Clp; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006514:Hepatitis B Surface Antigens / Q000235:genetics / Q000378:metabolism; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism*; D017510:Protein Folding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D006514:Hepatitis B Surface Antigens; D018832:Molecular Chaperones; D020033:Protein Isoforms; D011498:Protein Precursors; D011993:Recombinant Fusion Proteins; C050807:presurface protein 2, hepatitis B surface antigen; D001616:beta-Galactosidase; D049071:Endopeptidase Clp; C063842:dnaK protein, E coli; C069775:ClpB protein, E coli