The membrane perturbations caused by the interaction of p-azidobenzylphlorizin (p-AzBPhz), a potential photoaffinity labeling agent of the anion and d-glucose transporters in the human erythrocyte, have been studied using electron spin resonance (ESR) spectrometry. Two lipid-specific spin labels have been employed; one of these agents, a hexadecyl-quarternary amine with the nitroxide reporter group covalently attached to the cationic nitrogen, (CAT-16), has been used to monitor changes in the physical state of the membrane's extracellular phospholipid/water interface. The other spin label, 5-doxylstearic acid (5-NS), is designed to examine the order and motion of the lipid bilayer near the cell surface. In separate experiments, intact human red cells labeled with these lipid-specific spin labels were exposed to small amounts of the phlorizin azide. A dose-dependent alteration in CAT-16 motion was observed, but the p-AzBPhz interaction with the membrane had no effect on the spectrum of 5-NS. The half-maximal effect of the phlorizin derivative on the CAT-16 spectrum occurred when about 2 million molecules were bound to each cell. This is also the combined amount of band 3 and band 4.5 present in the red cell membrane and represents the concentration necessary to inhibit both anion and glucose transport. Our results suggest that the first p-AzBPhz molecules binding to the red cell membrane interact with the anion and sugar transporters, and not with the bulk lipid bilayer.
|Number of pages||5|
|Journal||BBA - Biomembranes|
|State||Published - Feb 13 1989|
Bibliographical noteFunding Information:
We thank Dr. Otto Frt~hlich for performing the chloride flux experiments and allowing us to incorporate the data into this manuscript. This work was supported in part by grants from the National Science Foundation (Grant R11-8610671) and the Commonwealth EPSCoR Program (D.A.B. and D.F.D.) and the Tobacco z:.,d Health Research Institute (D.A.B.).
- Anion transport protein
- Band 3
- Band 4.5
- Glucose transporter
ASJC Scopus subject areas
- Cell Biology