The arginine of the DRY motif in transmembrane segment III functions as a balancing micro-switch in the activation of the β2-adrenergic receptor
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Recent high resolution x-ray structures of the β2-adrenergic receptor confirmed a close salt-bridge interaction between the suspected micro-switch residue ArgIII:26 (Arg3.50) and the neighboring AspIII:25 (Asp3.49). However, neither the expected "ionic lock" interactions between ArgIII:26 and GluVI:-06 (Glu6.30) in the inactive conformation nor the interaction with TyrV:24 (Tyr5.58) in the active conformation were observed in the x-ray structures. Here we find through molecular dynamics simulations, after removal of the stabilizing T4 lysozyme, that the expected salt bridge between ArgIII:26 and GluVI:-06 does form relatively easily in the inactive receptor conformation. Moreover, mutational analysis of GluVI:-06 in TM-VI and the neighboring AspIII:25 in TM-III demonstrated that these two residues do function as locks for the inactive receptor conformation as we observed increased G(s) signaling, arrestin mobilization, and internalization upon alanine substitutions. Conversely, TyrV:24 appears to play a role in stabilizing the active receptor conformation as loss of function of G(s) signaling, arrestin mobilization, and receptor internalization was observed upon alanine substitution of TyrV:24. The loss of function of the TyrV:24 mutant could partly be rescued by alanine substitution of either AspIII:25 or GluVI:-06 in the double mutants. Surprisingly, removal of the side chain of the ArgIII:26 micro-switch itself had no effect on G(s) signaling and internalization and only reduced arrestin mobilization slightly. It is suggested that ArgIII:26 is equally important for stabilizing the inactive and the active conformation through interaction with key residues in TM-III, -V, and -VI, but that the ArgIII:26 micro-switch residue itself apparently is not essential for the actual G protein activation.
Original language | English |
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Journal | Journal of Biological Chemistry |
Volume | 287 |
Issue number | 38 |
Pages (from-to) | 31973-82 |
Number of pages | 10 |
ISSN | 0021-9258 |
DOIs | |
Publication status | Published - 14 Sep 2012 |
- Alanine, Amino Acid Motifs, Animals, Arginine, Arrestin, CHO Cells, COS Cells, Cell Membrane, Cercopithecus aethiops, Cricetinae, GTP-Binding Proteins, Gene Silencing, Models, Molecular, Molecular Dynamics Simulation, Mutagenesis, Site-Directed, Protein Binding, Receptors, Adrenergic, beta-2, Structure-Activity Relationship
Research areas
ID: 46290242