How proteins come together in the plasma membrane and function in macromolecular assemblies - Focus on receptor mosaics

Some theoretical aspects on structure and function of proteins have been discussed. Proteins form multimeric complexes since they have the capability of binding other proteins (Lego property) resulting in multimeric complexes capable of emergent functions. The distinction has been proposed between multimeric proteins according to their genomic or post-genomic origin. Proteins spanning the plasma membrane have been analysed by considering the effects of the micro-environment in which the protein is embedded. In particular, the different effects of the hydrophilic (extra-cellular and intracellular) versus the lipophilic (intra-membrane) environment has been considered. These aspects have be discussed in the frame of membrane micro-domains, in particular, the so called "rafts". In the alpha helix proteins the individual peptide dipoles align to produce a macro-dipole crossing the entire membrane. This macro-dipole has its positive (extra-cellular) pole at the amino-terminal end of helix and its negative (intracellular) pole at the carboxy-terminal. This arrangement has been analysed in the frame of the so-called counter-ion atmosphere that is the formation of a cloud of small ions bearing an opposite charge. Excitable cells reverse their resting potential during the all-or-none action potentials. Hence, the extra-cellular side of the plasma membrane becomes negative with respect the intracellular side. This change of polarization affects also the direction and magnitude of the alpha-helix dipole in view of the fact that there is a displacement of the counter-ions. The oscillation in the intensity of the dipole caused by the action potentials, opens the possibility of an interaction among dipoles by electromagnetic waves.