Beta2 adrenergic receptor activation. Modulation of the proline kink in transmembrane 6 by a rotamer toggle switch.
In many rhodopsin-like G-protein-coupled receptors, agonist binding to a cluster of aromatic residues in TM6 may promote receptor activation by altering the configuration of the TM6 Pro-kink and by the subsequent movement of the cytoplasmic end of TM6 away from TM3. We hypothesized that the highly conserved Cys(6.47), in the vicinity of the conserved Pro(6.50), modulates the configuration of the aromatic cluster and the TM6 Pro-kink through specific interactions in its different rotamer configurations. In the beta(2) adrenergic receptor, mutation of Cys(6.47) to Thr, which in an alpha-helix has a different rotamer distribution from Cys and Ser, produced a constitutively active receptor, whereas the Ser mutant was similar to wild-type receptor. Use of the biased Monte Carlo technique of Conformational Memories showed that the rotamer changes among Cys/Ser/Thr(6.47), Trp(6.48), and Phe(6.52) are highly correlated, representing a rotamer "toggle switch" that may modulate the TM6 Pro-kink. Differential modulation of the accessibility of Cys(6.47) and an engineered Cys(6.52) in wild type and a constitutively active background provides experimental support for the association of this rotamer switch with receptor activation.
Shi
Lei
L
Center for Molecular Recognition, Departments of Pharmacology and Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
Liapakis
George
G
Xu
Rui
R
Guarnieri
Frank
F
Ballesteros
Juan A
JA
Javitch
Jonathan A
JA
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D002460:Cell Line; D003545:Cysteine / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D011392:Proline / Q000378:metabolism*; D011412:Propanolamines / Q000494:pharmacology; D011487:Protein Conformation; D018343:Receptors, Adrenergic, beta-2 / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*
D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; D018343:Receptors, Adrenergic, beta-2; D011392:Proline; D003545:Cysteine; C033394:CGP 12177