Janovjak, Harald LIST Austria ; Struckmeier, Jens ; Hubain, Maurice ; Kessler, Max ; Kedrov, Alexej ; Mueller, Daniel J
The folding and stability of transmembrane proteins is a fundamental and unsolved biological problem. Here, single bacteriorhodopsin molecules were mechanically unfolded from native purple membranes using atomic force microscopy and force spectroscopy. The energy landscape of individual transmembrane α helices and polypeptide loops was mapped by monitoring the pulling speed dependence of the unfolding forces and applying Monte Carlo simulations. Single helices formed independently stable units stabilized by a single potential barrier. Mechanical unfolding of the helices was triggered by 3.9–7.7 Å extension, while natural unfolding rates were of the order of 10−3 s−1. Besides acting as individually stable units, helices associated pairwise, establishing a collective potential barrier. The unfolding pathways of individual proteins reflect distinct pulling speed-dependent unfolding routes in their energy landscapes. These observations support the two-stage model of membrane protein folding in which α helices insert into the membrane as stable units and then assemble into the functional protein.
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Janovjak HL, Struckmeier J, Hubain M, Kessler M, Kedrov A, Mueller D. Probing the energy landscape of the membrane protein bacteriorhodopsin. Structure. 2004;12(5):871-879. doi:10.1016/j.str.2004.03.016
Janovjak, H. L., Struckmeier, J., Hubain, M., Kessler, M., Kedrov, A., & Mueller, D. (2004). Probing the energy landscape of the membrane protein bacteriorhodopsin. Structure, 12(5), 871–879. https://doi.org/10.1016/j.str.2004.03.016
Janovjak, Harald L, Jens Struckmeier, Maurice Hubain, Max Kessler, Alexej Kedrov, and Daniel Mueller. “Probing the Energy Landscape of the Membrane Protein Bacteriorhodopsin.” Structure 12, no. 5 (2004): 871–79. https://doi.org/10.1016/j.str.2004.03.016.
H. L. Janovjak, J. Struckmeier, M. Hubain, M. Kessler, A. Kedrov, and D. Mueller, “Probing the energy landscape of the membrane protein bacteriorhodopsin,” Structure, vol. 12, no. 5, pp. 871–879, 2004.
Janovjak HL, Struckmeier J, Hubain M, Kessler M, Kedrov A, Mueller D. 2004. Probing the energy landscape of the membrane protein bacteriorhodopsin. Structure. 12(5), 871–879.
Janovjak, Harald L., et al. “Probing the Energy Landscape of the Membrane Protein Bacteriorhodopsin.” Structure, vol. 12, no. 5, Cell Press, 2004, pp. 871–79, doi:10.1016/j.str.2004.03.016.