Quantifying the Initial Unfolding of Bacteriorhodopsin Reveals Retinal Stabilization

Author
Abstract
The forces that stabilize membrane proteins remain elusive to precise quantification. Particularly important, but poorly resolved, are the forces present during the initial unfolding of a membrane protein, where the most native set of interactions is present. A high-precision, atomic force microscopy assay was developed to study the initial unfolding of bacteriorhodopsin. A rapid near-equilibrium folding between the first three unfolding states was discovered, the two transitions corresponded to the unfolding of five and three amino acids, respectively, when using a cantilever optimized for 2 μs resolution. The third of these states was retinal-stabilized and previously undetected, despite being the most mechanically stable state in the whole unfolding pathway, supporting 150 pN for more than 1 min. This ability to measure the dynamics of the initial unfolding of bacteriorhodopsin provides a platform for quantifying the energetics of membrane proteins under native-like conditions.
Year of Publication
2019
Journal
Angewandte Chemie
Volume
131
Number of Pages
1724-1727
Date Published
2019-01
URL
https://onlinelibrary.wiley.com/doi/full/10.1002/ange.201812072
DOI
10.1002/ange.v131.610.1002/ange.201812072
Journal Article