Transmembrane orientation of lipophilin in phosphatidylcholine vesicles
Lipophilin, a hydrophobic myelin protein, was incorporated into phosphatidylcholine vesicles by dialysis from 2-chloroethanol which has been shown to produce single-layered lipid-protein vesicles. These vesicles were labeled with a nonpenetrating surface-labeling reagent, 4,4′-diisothiocyano-2,2′-ditritiostilbene disulfonic acid, ([3H]DIDS), in order to determine if the protein completely spans the bilayer. After labeling the vesicles, lipophilin was isolated. At least 88% of the protein was labeled with [3H]DIDS. Dextran (mol wt 250,000–275,000) was converted to the dialdehyde form and reacted with lipophilin-PC vesicles. In this case greater than 90% of the protein was complexed to the dextran. The high degree of labeling obtained with both compounds was consistent with a model in which lipophilin was considered to span the bilayer completely.
KeywordsDextran Phosphatidylcholine Myelin Protein Disulfonic Acid Phosphatidylcholine Vesicle
Unable to display preview. Download preview PDF.
- 2.Vanderkooi, G., andGreen, D. E. 1971. New insights into biological membrane structure. Bioscience 21:409–415.Google Scholar
- 5.Vail, W. J., Papahadjopoulos, D., andMoscarello, M. A. 1974. The interaction of a hydrophobic protein with liposomes. Evidence for particles seen in freeze-fracture as being proteins. Biochim. Biophys. Acta 345:463–467.Google Scholar
- 8.Poduslo, J. F., andBraun, P. E. 1975., Topographical arrangement of membrane proteins in the intact myelin sheath. J. Biol. Chem. 250:1099–1105.Google Scholar
- 9.Golds, E., andBraun, P. E. 1976. Organization of membrane proteins in the intact myelin sheath. J. Biol. Chem. 251:4729–4735.Google Scholar
- 12.Cabantchik, Z. I., andRothstein, A 1974. Membrane proteins related to anion permeability of human red blood cells. J. Memb. Biol. 15:227–248.Google Scholar
- 16.Rand, R. P., Papahadjopoulos, D., andMoscarello, M. A. 1976. On the interaction of lecithins both with a purified hydrophobic protein from myelin and with fatty acids and lysolecithin. Biophys. J. 16:192a.Google Scholar