Premium
G‐protein alpha subunits differentially alter the conformation of kappa opioid receptor
Author(s) -
Yan Feng,
Roth Bryan
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a429-c
Subject(s) - chemistry , κ opioid receptor , receptor , agonist , stereochemistry , biophysics , g protein coupled receptor , helix (gastropod) , cysteine , g protein , biochemistry , biology , ecology , snail , enzyme
Kappa opioid receptors (KORs) represent the molecular target for the hallucinogenic agonist salvinorin A (Roth et al, PNAS 2002). The binding mode of KOR and salvinorin A was identified as a complex network of hydrogen bonds and hydrophobic interactions. It is well documented that small agonist molecule, such as salvinorin A, can induce the conformational changes of G protein coupled receptors, while there is very limited study about how other macromolecules (G‐proteins) affect receptor binding and function. In the present study, over‐expression of Gα16 and Gαi2 were used to increase the coupling rate between KOR and the G‐proteins. The substituted cysteine accessibility method (SCAM), utilizing the specific reaction between sulfhydryl group (‐SH) and 2‐minoethylmethanethiosulfonate (MTSEA), was applied to detect the conformational changes of the receptor. Significant conformational changes were observed on TM7, the top part of TM6 and EL2. Specific Gαi2 of KOR demonstrated a larger effect than the universal Gα16. Seven SCAM sensitive residues (S310, F314 to Y320) on TM7 presented a cluster pattern at the non‐G‐protein over‐expressed state of KOR and additional residues became sensitive upon over‐expressing various G proteins. The appearance of relative sensitive residues about every 4 residues shows the characteristic α‐helix pattern of TM7. In conclusion, there is no dramatic SCAM pattern changes observed due to G‐protein coupling, however, some conformations of the receptor are preferred by agonists over the others. Interestingly the moderate conformational changes induced by G‐protein have profound effects on agonist affinities. This conclusion is supported by the recently published activated rhodoposin structure. Supported by NIDA RO1DA 017204 and NIMH PDSP.