Origin of Increased Thermal Stability
The 10°C thermal stabilization of rhodopsin by a single engineered disulfide bond is striking. The N-terminus forms multiple contacts to the E1 and E2 loops, as well as to the ends of helices 1 and 3. Removal of the first 36 amino acids would thus excavate 974 Å2 of the residual receptors surface. The N2C/D282C disulfide bond fixes the position of this N-terminal cap and could increase stability by blocking specific unfolding pathways of the receptor. The restraining disulfide also prevents an opening of the N-terminal cap providing further evidence that the retinal is not entering through the extracellular side of the receptor.
Thermal Stability movie (Quicktime, H264, 2MB).
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