The chaperone function of ClpB from Thermus thermophilus depends on allosteric interactions of its two ATP-binding sites.
ClpB belongs to the Hsp100 family and assists de-aggregation of protein aggregates by DnaK chaperone systems. It contains two Walker consensus sequences (or P-Loops) that indicate potential nucleotide binding domains (NBD). Both domains appear to be essential for chaperoning function, since mutation of the conserved lysine residue of the GX(4)GKT consensus sequences to glutamine (K204Q and K601Q) abolishes its properties to accelerate renaturation of aggregated firefly luciferase. The underlying biochemical reason for this malfunction appears not to be a dramatically reduced ATPase activity of either P-loop per se but rather changed properties of co-operativity of ATPase activity connected to oligomerization properties to form productive oligomers. This view is corroborated by data that show that structural stability (as judged by CD spectroscopy) or ATPase activity at single turnover conditions (at low ATP concentrations) are not significantly affected by these mutations. In addition nucleotide binding properties of wild-type protein and mutants (as judged by binding studies with fluorescent nucleotide analogues and competitive displacement titrations) do not differ dramatically. However, the general pattern of formation of stable, defined oligomers formed as a function of salt concentration and nucleotides and more importantly, cooperativity of ATPase activity at high ATP concentrations is dramatically changed with the two P-loop mutants described.
Schlee
S
S
Abteilung physikalische Biochemie, Max-Planck-Institut für molekulare Physiologie, Otto-Hahn-Strasse 11, Dortmund, D-44227, Germany.
Groemping
Y
Y
Herde
P
P
Seidel
R
R
Reinstein
J
J
D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000494:Allosteric Regulation; D000495:Allosteric Site; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000378:metabolism; D049071:Endopeptidase Clp; D004789:Enzyme Activation; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006358:Hot Temperature; D006868:Hydrolysis; D007700:Kinetics; D008156:Luciferases / Q000737:chemistry / Q000378:metabolism; D018832:Molecular Chaperones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D009994:Osmolar Concentration; D011485:Protein Binding; D011489:Protein Denaturation; D020673:Protein Renaturation; D017434:Protein Structure, Tertiary; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics; D016963:Thermus thermophilus / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D062367:ortho-Aminobenzoates / Q000378:metabolism
D001426:Bacterial Proteins; 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; D018832:Molecular Chaperones; D062367:ortho-Aminobenzoates; D000244:Adenosine Diphosphate; C081523:3'-O-(N-methylanthraniloyl)adenosine 5'-diphosphate; D000255:Adenosine Triphosphate; D008156:Luciferases; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C063842:dnaK protein, E coli; C069775:ClpB protein, E coli