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Oligomerization of the fifth transmembrane domain from the adenosine A 2A receptor
Author(s) -
Thévenin Damien,
Lazarova Tzvetana,
Roberts Matthew F.,
Robinson Clifford R.
Publication year - 2005
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.051409205
Subject(s) - transmembrane domain , förster resonance energy transfer , circular dichroism , chemistry , g protein coupled receptor , peptide , folding (dsp implementation) , transmembrane protein , helix (gastropod) , dimer , biophysics , crystallography , protein secondary structure , membrane protein , stereochemistry , receptor , membrane , biology , biochemistry , fluorescence , ecology , physics , organic chemistry , quantum mechanics , snail , electrical engineering , engineering
The human adenosine A 2A receptor (A 2A R) belongs to one of the largest family of membrane proteins, the G‐protein coupled receptors (GPCRs), characterized by seven transmembrane (TM) helices. Little is known about the determinants of their structures, folding, assembly, activation mechanisms, and oligomeric states. Previous studies in our group showed that peptides corresponding to all seven TM domains form stable helical structures in detergent micelles and lipid vesicles. However, the peptides behave differently; TM5 is the only peptide to have a ratio [θ] 222 /[θ] 208 obtained by circular dichroism (CD) spectroscopy>1. This finding suggested to us that TM5 might self‐associate. In the present study, we investigate the unique properties of the TM5 domain. We performed detailed analyses of TM5 peptide behavior in membrane‐mimetic environments using CD spectroscopy, fluorescence spectroscopy and Förster resonance energy transfer, and gel electrophoresis. We find that TM5 peptide has the ability to self‐associate to form oligomeric structures in various hydrophobic milieus and that these oligomers are highly resistant to temperature and chemical denaturation. We also find that mutation of the full‐length A 2A R at position M193, which is located in the fifth TM domain, noticeably alters A 2A R monomer: dimer ratio as observed on SDS‐PAGE. Our results suggest that parallel association of TM5 dimers may play a role in the known adenosine A 2A receptor dimerization. This study represents the first evidence of an individual GPCR transmembrane domain self‐association.