Measurement of intermolecular distances for the natural agonist Peptide docked at the cholecystokinin receptor expressed in situ using fluorescence resonance energy transfer.
Mol Pharmacol
; 65(1): 28-35, 2004 Jan.
Article
em En
| MEDLINE
| ID: mdl-14722234
ABSTRACT
Fluorescence resonance energy transfer is a powerful biophysical technique used to analyze the structure of membrane proteins. Here, we used this tool to determine the distances between a distinct position within a docked agonist and a series of distinct sites within the intramembranous confluence of helices and extracellular loops of the cholecystokinin (CCK) receptor. Pseudo-wild-type CCK receptor constructs having single reactive cysteine residues inserted into each of these sites were developed. The experimental strategy included the use of the full agonist, Alexa488-CCK, bound to these receptors as donor, with Alexa568 covalently bound to the specific sites within the CCK receptor as acceptor. Site-labeling was achieved by derivatization of intact cells with a novel fluorescent methanethiosulfonate reagent. A high degree of spectral overlap was observed between receptor-bound donor and receptor-derivatized acceptors, with no transfer observed for a series of controls representing saturation of the receptor binding site with nonfluorescent ligand and use of a null-reactive CCK receptor construct. The measured distances between the fluorophore within the docked agonist and the sites within the first (residue 102) and third (residue 341) extracellular loops of the receptor were shorter than those directed to the second loop (residue 204) or to intramembranous helix two (residue 94). These distances were accommodated well within a refined molecular model of the CCK-occupied receptor that is fully consistent with all existing structure-activity and photoaffinity-labeling studies. This approach provides the initial insights into the conformation of extracellular loop regions of this receptor and establishes clear differences from analogous loops in the rhodopsin crystal structure.
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Coleções:
01-internacional
Temas:
Geral
Base de dados:
MEDLINE
Assunto principal:
Colecistocinina
/
Receptores da Colecistocinina
/
Transferência Ressonante de Energia de Fluorescência
Limite:
Animals
Idioma:
En
Revista:
Mol Pharmacol
Ano de publicação:
2004
Tipo de documento:
Article
País de afiliação:
Estados Unidos