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Abstract
Adrenergic receptors are integral membrane proteins involved in cellular signalling that belong to the G protein-coupled receptors. Synthetic peptides resembling the putative transmembrane (TM) segments TM4, TM6 and TM7, of the human α2-adrenergic receptor subtype C10 (P08913) and defined lipid vesicles were used to assess protein-lipid interactions that might be relevant to receptor structure/function. P6 peptide contains the hydrophobic core of TM6 plus the N-terminal hydrophilic motif REKR, while peptides P4 and P7 contained just the hydrophobic stretches of TM4 and TM7, respectively. All the peptides increase their helical tendency at moderate concentrations of TFE (30–50%) and in presence of 1,2-dielaidoyl-sn-glycero-3-phosphatidylethanolamine (DEPE) lipids. However, only P6 displays up to 19% of α-helix in the presence of just the DEPE lipids, evidences a transmembrane orientation and stabilizes the Lα lipid phase. Conversely, P4 and P7 peptides form only stable β-sheet structures in DEPE and favour the non-lamellar, inverted hexagonal (HII) phase of DEPE by lowering its phase transition temperature. This study highlights the potential of using synthetic peptides derived from the amino acid sequence in the native proteins as templates to understand the behaviour of the transmembrane segments and underline the importance of interfacial anchoring interactions to meet hydrophobic matching requirements and define membrane organization.
| Abbreviations | ||
| GPCR | = | G protein-coupled receptor |
| AR | = | Adrenergic receptor |
| α2-AR | = | α2-adrenergic receptor |
| TM | = | transmembrane segment |
| TMH | = | membrane-spanning α-helix |
| PE | = | phosphatidylethanolamine |
| DEPE | = | 1,2-dielaidoyl-sn-glycero-3-phosphatidylethanolamine |
| DPPC | = | 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine |
| MLV | = | multilamellar lipid vesicles |
| Lβ | = | gel lamellar phase |
| Lα | = | liquid-crystalline lamellar phase |
| HII | = | inverted hexagonal phase |
| d | = | lattice space |
| Tm | = | gel-to-liquid lamellar phase transition temperature |
| TH | = | lamellar-to-inverted hexagonal phase transition temperature |
| Abbreviations | ||
| GPCR | = | G protein-coupled receptor |
| AR | = | Adrenergic receptor |
| α2-AR | = | α2-adrenergic receptor |
| TM | = | transmembrane segment |
| TMH | = | membrane-spanning α-helix |
| PE | = | phosphatidylethanolamine |
| DEPE | = | 1,2-dielaidoyl-sn-glycero-3-phosphatidylethanolamine |
| DPPC | = | 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine |
| MLV | = | multilamellar lipid vesicles |
| Lβ | = | gel lamellar phase |
| Lα | = | liquid-crystalline lamellar phase |
| HII | = | inverted hexagonal phase |
| d | = | lattice space |
| Tm | = | gel-to-liquid lamellar phase transition temperature |
| TH | = | lamellar-to-inverted hexagonal phase transition temperature |