Conformational rearrangements of tail-less complex polypeptide 1 (TCP-1) ring complex (TRiC)-bound actin.
The mechanism of chaperonins is still under intense investigation. Earlier studies by others and us on the bacterial chaperonin GroEL points to an active role of chaperonins in unfolding the target protein during initial binding. Here, a natural eukaryotic chaperonin system [tail-less complex polypeptide 1 (TCP-1) ring complex (TRiC) and its target protein actin] was investigated to determine if the active participation of the chaperonin in the folding process is evolutionary-conserved. Using fluorescence resonance energy transfer (FRET) measurements on four distinct doubly fluorescein-labeled variants of actin, we have obtained a fairly detailed map of the structural rearrangements that occur during the TRiC-actin interaction. The results clearly show that TRiC has an active role in rearranging the bound actin molecule. The target is stretched as a consequence of binding to TRiC and further rearranged in a second step as a consequence of ATP binding; i.e., the mechanism of chaperonins is conserved during evolution.
Villebeck
Laila
L
Division of Molecular Biotechnology, IFM, Linköping University, Linköping 58183, Sweden.
Persson
Malin
M
Luan
Shi-Lu
SL
Hammarström
Per
P
Lindgren
Mikael
M
Jonsson
Bengt-Harald
BH
D000199:Actins / Q000737:chemistry*; D056404:Chaperonin Containing TCP-1; D018833:Chaperonins / Q000737:chemistry*; D003001:Cloning, Molecular; D004591:Electrophoresis, Polyacrylamide Gel; D031541:Fluorescence Resonance Energy Transfer; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation
D000199:Actins; D056404:Chaperonin Containing TCP-1; D018833:Chaperonins