ATP-enhanced molecular chaperone functions of the small heat shock protein human alphaB crystallin.
We report direct experimental evidence that human alphaB-crystallin, a member of the small heat shock protein family, actively participates in the refolding of citrate synthase (CS) in vitro. In the presence of 3.5 mM ATP, CS reactivation by alphaB-crystallin was enhanced approximately twofold. Similarly, 3.5 mM ATP enhanced the chaperone activity of alphaB-crystallin on the unfolding and aggregation of CS at 45 degrees C. Consistent with these findings, cell viability at 50 degrees C was improved nearly five orders of magnitude in Escherichia coli expressing alphaB-crystallin. SDS/PAGE analysis of cell lysates suggested that alphaB-crystallin protects cells against physiological stress in vivo by maintaining cytosolic proteins in their native and functional conformations. This report confirms the action of alphaB-crystallin as a molecular chaperone both in vitro and in vivo and describes the enhancement of alphaB-crystallin chaperone functions by ATP.
Muchowski
P J
PJ
Department of Biological Structure, Box 357420, University of Washington, Seattle, WA, 98195-7420, USA.
Clark
J I
JI
D000255:Adenosine Triphosphate / Q000502:physiology*; D002470:Cell Survival; D018834:Chaperonin 60 / Q000502:physiology; D002950:Citrate (si)-Synthase / Q000502:physiology; D003459:Crystallins / Q000502:physiology*; D004789:Enzyme Activation; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins / Q000502:physiology; D006360:Heat-Shock Proteins / Q000502:physiology*; D006801:Humans; D018832:Molecular Chaperones / Q000502:physiology*; D011487:Protein Conformation; D017510:Protein Folding; D013050:Spectrometry, Fluorescence
D018834:Chaperonin 60; D003459:Crystallins; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D000255:Adenosine Triphosphate; D002950:Citrate (si)-Synthase; C063842:dnaK protein, E coli