Kinetics of molecular chaperone action.
Molecular chaperones of the Hsp70 type transiently sequester unfolded segments of proteins and promote their correct folding. Target peptides were labeled with an environmentally sensitive fluorophore so that their binding to the molecular chaperone DnaK of Escherichia coli could be followed in real time. The two-step process was characterized by relaxation times of 27 seconds and 200 seconds with 2 microM DnaK and 0.1 microM ligand at 25 degrees C. In the presence of adenosine triphosphate, the formation of the complex was greatly accelerated and appeared to be a single-exponential process with a relaxation time of 0.4 second. The binding-release cycle of DnaK thus occurs in the time range of polypeptide chain elongation and folding and is too fast to be stoichiometrically coupled to the adenosine triphosphatase activity of the chaperone (turnover number, 0.13 per minute at 30 degrees C).
Schmid
D
D
Biochemisches Institut, Universität Zürich, Switzerland.
Baici
A
A
Gehring
H
H
Christen
P
P
D015081:2-Naphthylamine / Q000031:analogs & derivatives; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000595:Amino Acid Sequence; D001219:Aspartate Aminotransferases / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D004792:Enzyme Precursors / Q000378:metabolism; D029968:Escherichia coli Proteins; D005456:Fluorescent Dyes; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism*
D001426:Bacterial Proteins; D004792:Enzyme Precursors; D029968:Escherichia coli Proteins; D005456:Fluorescent Dyes; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D010446:Peptide Fragments; C022571:adenosine 5'-O-(3-thiotriphosphate); C038518:acrylodan; D000255:Adenosine Triphosphate; D015081:2-Naphthylamine; D001219:Aspartate Aminotransferases; D000251:Adenosine Triphosphatases; C063842:dnaK protein, E coli