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Regul Pept. 2009 Nov 27;158(1-3):110-5. doi: 10.1016/j.regpep.2009.05.007. Epub 2009 May 18.

Effects of pH and temperature on photoaffinity labeling of Family B G protein-coupled receptors.

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Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, 13400 East Shea Boulevard, Scottsdale, AZ 85259, USA.


The efficiency of covalent labeling of a receptor by a photolabile analogue of its natural ligand is dependent on the spatial approximation of the probe and its target. Systematic application of intrinsic photoaffinity labeling to the secretin receptor, a prototypic Family B G protein-coupled receptor, demonstrated reduced efficiency of labeling for amino-terminal and mid-region sites of labeling relative to carboxyl-terminal sites. Reduction of pH from 7.4 to 5.5 and reduction of temperature from 25 degrees C to 4 degrees C improved the efficiency of covalent labeling of the receptor with these probes. This correlated with sites of labeling at the interface between the receptor amino terminus and the receptor core, a region containing histidine residues that have their ionization affected in this pH range. Application to the calcitonin receptor, another Family B G protein-coupled receptor, yielded analogous results. These results support the consistent mode of docking peptide ligands to this group of receptors.

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