Characterization of Denatured States and Reversible Unfolding of Sensory Rhodopsin II.
Journal of molecular biology
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Tan, Y. L., Mitchell, J., Klein-Seetharaman, J., & Nietlispach, D. (2018). Characterization of Denatured States and Reversible Unfolding of Sensory Rhodopsin II.. Journal of molecular biology, 430 (21), 4068-4086. https://doi.org/10.1016/j.jmb.2018.07.031
Our understanding on the folding of membrane proteins lags behind that of soluble proteins due to challenges posed by the exposure of hydrophobic regions during in vitro chemical denaturation and refolding experiments. While different folding models are accepted for soluble proteins, only the two-stage model and the long-range interactions model have been proposed so far for helical membrane proteins. To address our knowledge gap on how different membrane proteins traverse their folding pathways, we have systematically investigated the structural features of SDS-denatured states and the kinetics for reversible unfolding of sensory rhodopsin II (pSRII), a retinal-binding photophobic receptor from Natronomonas pharaonis. pSRII is difficult to denature, and only SDS can dislodge the retinal chromophore without rapid aggregation. Even in 30% SDS (0.998 ΧSDS) pSRII retains the equivalent of six out of seven transmembrane helices, while the retinal binding pocket is disrupted, with transmembrane residues becoming more solvent-exposed. Folding of pSRII from an SDS-denatured state harbouring a covalently-bound retinal chromophore shows deviations from an apparent two-state behaviour. SDS-denaturation to form the sensory opsin apo-protein is reversible. We report pSRII as a new model protein which is suitable for membrane protein folding studies, and has a unique folding mechanism that differs from those of bacteriorhodopsin and bovine rhodopsin.
Animals, Cattle, Bacteriorhodopsins, Sensory Rhodopsins, Solvents, Protein Conformation, Protein Structure, Tertiary, Protein Binding, Protein Denaturation, Protein Folding, Kinetics, Protein Unfolding, Protein Refolding
External DOI: https://doi.org/10.1016/j.jmb.2018.07.031
This record's URL: https://www.repository.cam.ac.uk/handle/1810/284746
Attribution-NonCommercial-NoDerivatives 4.0 International
Licence URL: http://creativecommons.org/licenses/by-nc-nd/4.0/