A NMR investigation on the interactions of the alpha-oligomeric form of the M13 coat protein with lipids, which mimic the Escherichia coli inner membrane.

The interaction of the M13 bacteriophage major coat protein in the alpha-oligomeric form with specifically deuterated phospholipid headgroups which mimic the Escherichia coli inner membrane, has been studied using NMR methods. As can be seen from the deuterium NMR spectra obtained with headgroup trimethyl deuterated DOPC, the coat protein in the alpha-oligomeric form does not give rise to trapped lipids as observed with M13 coat protein in the beta-polymeric form (Van Gorkom et al. (1990) Biochemistry 29, 3828-3834). The quadrupolar splittings of the alpha headgroup methylene deuterons of deuterated phosphatidylcholine and phosphatidylethanolamine decrease, whereas the quadrupolar splittings of the beta headgroup methylene deuterons of the two lipids increase with increasing protein content. All deuterated segments in the phosphatidylglycerol headgroup show the same relative decrease of the NMR quadrupolar splittings. These results are interpreted in terms of a change in torsion angles of the methylene groups, induced by positive charges, probably lysine residues of the protein at the membrane surface. For all lipid bilayer compositions studied the head-group perturbations are similar. It is concluded that there is no strong specific interaction between one of the lipid types examined and the M13 coat protein. From the spin-spin (T2e) relaxation time and spin-lattice (T1z) relaxation time of all deuterated lipids it is concluded that at the bilayer surface only slow motions are affected by the M13 coat protein.