Interfacial properties of the M1 segment of the nicotinic acetylcholine receptor

AMBROGGIO, ERNESTO E.; VILLARREAL, MARCOS A.; MONTICH, GUILLERMO G.; RIJKERS, DIRK TS; DE PLANQUE, MAURITS R.R.; SEPAROVIC, FRANCES; FIDELIO, GERARDO D.

BIOPHYSICAL CHEMISTRY

Año: 2006 vol. 121 p. 171 - 176

0301-4622

We have studied the thermodynamic, surface, and structural properties of alphaM1 transmembrane sequence of the nicotinic acetylcholine receptor (nAChR) by using Langmuir monolayer, FT-IR spectroscopy and molecular dynamics simulation techniques in membrane-mimicking environments. M1 spontaneously incorporates into a lipid-free air-water interface, showing a favourable adsorption free energy of -7.2 kcal/mol. A cross-sectional molecular area of 210 A(2)/molecule, a surface potential of 4.2 fV/molecule and a high stability of the film were deducted from pure M1 monolayers. FT-IR experiments and molecular dynamics simulations in membrane-mimicking environments (sodium-dodecyl-sulfate and CCl(4), respectively) indicate coexistence between helical and non-helical structures. Furthermore, mixed peptide-lipid monolayers and monolayer penetration experiments were performed in order to study the peptide-lipid interaction. Mixed with condensed lipids (dipalmitoyl-phosphocholine, and dipalmitoyl-phosphoglycerol), M1 shows immiscible/miscible behaviour at low/high peptide concentration, respectively. Conversely, a complete miscible peptide-lipid interface is observed with liquid-expanded lipids (palmitoyl-oleoyl-phosphocholine, and palmitoyl-oleoyl-phosphoglycerol). Peptide penetration experiments demonstrate that the M1 peptide preferentially interacts with zwitterionic phosphocholine interfaces.