The effects of the membrane-penetrating polypeptide segment of the human erythrocyte MN-glycoprotein on the permeability of model lipid membranes.

The insoluble peptide, T(is), prepared by trypsin hydrolysis of the MN-glycoprotein (glycophorin) of the human erythrocyte has been incorporated into phospholipid membranes in the form of liposomes and black lipid membranes. The permeability of liposome membranes to 42K+ and of black lipid membranes to water and ions is increased significantly by the presence of the T(is) peptide. Electrophoresis measurements indicate that these effects are not due to the T(is) peptide carrying a net charge. The results suggest that the peptide causes local disordering of the bilayer membrane structures. This is considered in the light of findings published elsewhere: that the MN-glycoprotein penetrates through the cell membrane via a non-polar segment of its polypeptide chain, which is contained intact within the T(is) peptide; that the T(is) peptide is partially helical when associated with phospholipid and forms multimeric 8.0 nm structures within the hydrophobic plane of phospholipid bilayers.