[beta] sub(2) Adrenergic Receptor Activation. MODULATION OF THE PROLINE KINK IN TRANSMEMBRANE 6 BY A ROTAMER TOGGLE SWITCH

• Published in: The Journal of biological chemistry Vol. 277; no. 43; pp. 40989 - 40996
• Main Authors: Shi, L, Liapakis, G, Xu, R, Guarnieri, F, Ballesteros, JA, Javitch, JA
• Format: Journal Article
• Language: English
• Published: 25.10.2002
• ISSN: 0021-9258

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 super(6.47), in the vicinity of the conserved Pro super(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] sub(2) adrenergic receptor, mutation of Cys super(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 super(6.47), Trp super(6.48), and Phe super(6.52) are highly correlated, representing a rotamer "toggle switch" that may modulate the TM6 Pro-kink. Differential modulation of the accessibility of Cys super(6.47) and an engineered Cys super(6.52) in wild type and a constitutively active background provides experimental support for the association of this rotamer switch with receptor activation.