Direct observation of chaperone-induced changes in a protein folding pathway.
How chaperone interactions affect protein folding pathways is a central problem in biology. With the use of optical tweezers and all-atom molecular dynamics simulations, we studied the effect of chaperone SecB on the folding and unfolding pathways of maltose binding protein (MBP) at the single-molecule level. In the absence of SecB, we find that the MBP polypeptide first collapses into a molten globulelike compacted state and then folds into a stable core structure onto which several alpha helices are finally wrapped. Interactions with SecB completely prevent stable tertiary contacts in the core structure but have no detectable effect on the folding of the external alpha helices. It appears that SecB only binds to the extended or molten globulelike structure and retains MBP in this latter state. Thus during MBP translocation, no energy is required to disrupt stable tertiary interactions.
Department of Molecular Microbiology, Groningen Bio-molecular Sciences and Biotechnology Institute and the Zernike Institute for Advanced Materials, University of Groningen, Kerklaan 30, 9751 NN Haren, Netherlands.
Philipp
P
Bechtluft
Ruud G H
RG
van Leeuwen
Matthew
M
Tyreman
Danuta
D
Tomkiewicz
Nico
N
Nouwen
Harald L
HL
Tepper
Arnold J M
AJ
Driessen
Sander J
SJ
Tans
D001426:Bacterial Proteins / Q000378:metabolism*; D003198:Computer Simulation; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D052898:Optical Tweezers; D033902:Periplasmic Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C461619:MalE protein, E coli; D033902:Periplasmic Binding Proteins; C057842:SecB protein, Bacteria