@article {Carrillo1123, author = {Juan J. Carrillo and Juan F. L{\'o}pez-Gim{\'e}nez and Graeme Milligan}, title = {Multiple Interactions between Transmembrane Helices Generate the Oligomeric α1b-Adrenoceptor}, volume = {66}, number = {5}, pages = {1123--1137}, year = {2004}, doi = {10.1124/mol.104.001586}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {Combinations of coimmunoprecipitation, single-cell fluorescence resonance energy transfer, and cell-surface time-resolved fluorescence resonance energy transfer demonstrated protein-protein interactions and quaternary structure for the α1b-adrenoceptor. Self-association of transmembrane domain 1 and its interaction with the full-length receptor indicated a symmetrical interface provided by this domain. Lack of effect of mutation of the glycophorin-A dimerization-like region within this helix demonstrated that this did not provide the molecular mechanism. Multiple interactions were observed between the α1b-adrenoceptor and fragments derived from its sequence. Fragments comprising transmembrane domains 3 and 4 and transmembrane domains 5 and 6, but not transmembrane domain 7, were also able to interact with the full-length receptor. Transmembrane domain 7 failed to interact significantly with any element of the receptor and was not transported to the cell surface after coexpression with the full-length receptor. Symmetrical interactions were also noted between fragments incorporating transmembrane domain 4, but this segment of the receptor failed to interact with transmembrane domains 1 and 2 or transmembrane domains 5 and 6. Time-resolved fluorescence resonance energy transfer studies were also consistent with contributions of transmembrane domains 1 and/or 2 and transmembrane domains 3 and/or 4 to protein-protein interactions within the quaternary structure of the α1b-adrenoceptor, and with a contribution of transmembrane domains 5 and/or 6. These data are consistent with a complex oligomeric quaternary structure of the α1b-adrenoceptor in which major, symmetrical interactions may define intradimeric contacts with other contributions, providing interdimer contacts to generate oligomeric complexes akin to those observed for murine rhodopsin. A model derived from this was developed.}, issn = {0026-895X}, URL = {https://molpharm.aspetjournals.org/content/66/5/1123}, eprint = {https://molpharm.aspetjournals.org/content/66/5/1123.full.pdf}, journal = {Molecular Pharmacology} }