INTERACTION OF 2 COMPLEMENTARY FRAGMENTS OF THE BOVINE SPINAL-CORD MYELIN BASIC-PROTEIN WITH PHOSPHATIDYLGLYCEROL BILAYERS, STUDIED BY H-2 AND P-31 NMR-SPECTROSCOPY

The interaction of two complementary fragments of myelin basic protein from bovine spinal cord with bilayers of dimyristoylphosphatidylglyce rol has been studied by broad line H-2 and P-31 NMR. The fragments, pr oduced by cleavage at the single tryptophan, consist of an N-terminal portion of molecular mass 12.6 kDa and a C-terminal portion of molecul ar mass 5.8 kDa. The phosphatidylglycerol lipid was deuterated at all three segments of the glycerol headgroup. The approximately linear dep endence of the H-2 quadrupole splittings and P-31 chemical shift aniso tropy on protein/lipid ratio in the complexes indicates that the lipid s interacting with the protein fragments were in fast exchange on the NMR time scale (almost-equal-to 10(-4)-10(-5) s). The relative gradien ts of the dependence on protein/lipid ratio of both these parameters d ecrease with the size of the protein fragment and correlate reasonably well with both the net charge on the protein and the lipid binding st oichiometries in the absence of salt. The results are therefore consis tent with a model in which the perturbation of the quadrupole splittin gs either is determined by the net surface potential or is constant fo r the different protein fragments. Either possibility is consistent wi th the reduced activity of the fragments relative to the whole protein .