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Active Cage Mechanism of Chaperonin-Assisted Protein Folding Demonstrated at Single-Molecule Level

MPG-Autoren
http://pubman.mpdl.mpg.de/cone/persons/resource/persons131134

Gupta,  Amit J.
Hartl, Franz-Ulrich / Cellular Biochemistry, Max Planck Institute of Biochemistry, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons134754

Haldar,  Shubhasis
Hartl, Franz-Ulrich / Cellular Biochemistry, Max Planck Institute of Biochemistry, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons134752

Milicic,  Goran
Hartl, Franz-Ulrich / Cellular Biochemistry, Max Planck Institute of Biochemistry, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons78072

Hartl,  F. Ulrich
Hartl, Franz-Ulrich / Cellular Biochemistry, Max Planck Institute of Biochemistry, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons78078

Hayer-Hartl,  Manajit
Hayer-Hartl, Manajit / Chaperonin-assisted Protein Folding, Max Planck Institute of Biochemistry, Max Planck Society;

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Zitation

Gupta, A. J., Haldar, S., Milicic, G., Hartl, F. U., & Hayer-Hartl, M. (2014). Active Cage Mechanism of Chaperonin-Assisted Protein Folding Demonstrated at Single-Molecule Level. JOURNAL OF MOLECULAR BIOLOGY, 426(15), 2739-2754. doi:10.1018/j.jmb.2014.04.018.


Zitierlink: http://hdl.handle.net/11858/00-001M-0000-0023-DAFF-4
Zusammenfassung
The cylindrical chaperonin GroEL and its lid-shaped cofactor GroES of Escherichia coil have an essential role in assisting protein folding by transiently encapsulating non-native substrate in an ATP-regulated mechanism. It remains controversial whether the chaperonin system functions solely as an infinite dilution chamber, preventing off-pathway aggregation, or actively enhances folding kinetics by modulating the folding energy landscape. Here we developed single-molecule approaches to distinguish between passive and active chaperonin mechanisms. Using low protein concentrations (100 pM) to exclude aggregation, we measured the spontaneous and GroEL/ES-assisted folding of double-mutant maltose binding protein (DM-MBP) by single-pair fluorescence resonance energy transfer and fluorescence correlation spectroscopy. We find that GroEL/ES accelerates folding of DM-MBP up to 8-fold over the spontaneous folding rate. Accelerated folding is achieved by encapsulation of folding intermediate in the GroEL/ES cage, independent of repetitive cycles of protein binding and release from GroEL. Moreover, photoinduced electron transfer experiments provided direct physical evidence that the confining environment of the chaperonin restricts polypeptide chain dynamics. This effect is mediated by the net-negatively charged wall of the GroEL/ES cavity, as shown using the GroEL mutant EL(KKK2) in which the net-negative charge is removed. EL(KKK2)/ES functions as a passive cage in which folding occurs at the slow spontaneous rate. Taken together our findings suggest that protein encapsulation can accelerate folding by entropically destabilizing folding intermediates, in strong support of an active chaperonin mechanism in the folding of some proteins. Accelerated folding is biologically significant as it adjusts folding rates relative to the speed of protein synthesis. (C) 2014 The Authors. Published by Elsevier Ltd.