Roles of individual domains and conserved motifs of the AAA+ chaperone ClpB in oligomerization, ATP hydrolysis, and chaperone activity.
ClpB of Escherichia coli is an ATP-dependent ring-forming chaperone that mediates the resolubilization of aggregated proteins in cooperation with the DnaK chaperone system. ClpB belongs to the Hsp100/Clp subfamily of AAA+ proteins and is composed of an N-terminal domain and two AAA-domains that are separated by a "linker" region. Here we present a detailed structure-function analysis of ClpB, dissecting the individual roles of ClpB domains and conserved motifs in oligomerization, ATP hydrolysis, and chaperone activity. Our results show that ClpB oligomerization is strictly dependent on the presence of the C-terminal domain of the second AAA-domain, while ATP binding to the first AAA-domains stabilized the ClpB oligomer. Analysis of mutants of conserved residues in Walker A and B and sensor 2 motifs revealed that both AAA-domains contribute to the basal ATPase activity of ClpB and communicate in a complex manner. Chaperone activity strictly depends on ClpB oligomerization and the presence of a residual ATPase activity. The N-domain is dispensable for oligomerization and for the disaggregating activity in vitro and in vivo. In contrast the presence of the linker region, although not involved in oligomerization, is essential for ClpB chaperone activity.
Mogk
Axel
A
Zentrum für Molekulare Biologie Heidelberg, Im Neuenheimer Feld 282, Heidelberg D-69120, Germany. a.mogk@zmbh-uni-heidelberg.de
Schlieker
Christian
C
Strub
Christine
C
Rist
Wolfgang
W
Weibezahn
Jimena
J
Bukau
Bernd
B
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D020816:Amino Acid Motifs; D002845:Chromatography; D017124:Conserved Sequence; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D049071:Endopeptidase Clp; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism*; D006868:Hydrolysis; D008156:Luciferases / Q000378:metabolism; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship; D013997:Time Factors; D014364:Tryptophan / Q000494:pharmacology
D003432:Cross-Linking Reagents; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D014364:Tryptophan; D000255:Adenosine Triphosphate; D008156:Luciferases; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C069775:ClpB protein, E coli