Cytosohc extracts of trout and turkey erythrocytes were tested for their lmmunoreactlvlty with polyclonal and monoclonal antlbodles to retmal arrestm (S-antigen), a cytosohc protem of photoreceptor cells involved m the desensltlzatlon of rhodopsm After adsorption or lmmunoaffimty chromatography of the extracts, these antibodies specifically recognized a protem having a molecular weight slmdar to that of retinal arrestm Because the G-protem-medlated transduction systems, such as visual and P-adrenerglc systems, display a high degree of structural and functlonal homology, the presence of arrestm-hke protems m non-photosensltlve cells suggests that these protems are Involved m the transduction of chemical signals, with a possible role m receptor desensltlzatlon Arrestm, Retmal S-antigen, Erythrocyte, /%Adrenerglc transduction, Phototransductlon, (Trout, Turkey)

The anion transport protein of the human erythrocyte membrane, band 3, was solubilized and purified in solutions of the non-ionic detergent Triton X-100. It was incorporated into spherical lipid bilayers by the following procedure: Dry phosphatidylcholine was suspended in the protein solution. Octylglucopyranoside was added until the milky suspension became clear. The sample was dialyzed overnight against detergent-free buffer. Residual Triton X-100 was removed from the opalescent vesicle suspension by sucrose density gradient centrifugation and subsequent dialysis. Sulfate efflux from the vesicles was studied, under exchange conditions, using a filtration method. Three vesicle subpopulations could be distinguished by analyzing the time course of the efflux. One was nearly impermeable to sulfate, and efflux from another was due to leaks. The largest subpopulation, however, showed transport characteristics very similar to those of the anion transport system of the intact erythrocyte membrane: transport numbers (at 30 degrees C) close to 20 sulfate molecules per band 3 and min, an activation energy of approx. 140 kJ/mol, a pH maximum at pH 6.2, saturation of the sulfate flux at sulfate concentrations around 100 mM, inhibition of the flux by H2DIDS and flufenamate (approx. KI-values at 30 degrees C: 0.1 and 0.7 microM, respectively), and "right-side-out" orientation of the transport protein (as judged from the inhibition of sulfate efflux by up to 98% by externally added H2DIDS). Thus, the system represents, for the first time, a reconstitution of all the major properties of the sulfate transport across the erythrocyte membrane.

No abstract

The anion transport system of the human erythrocyte membrane was reconstituted in unilamellar phosphatidylcholine vesicles, and a vesicle subpopulation of a narrow size distribution was isolated from the sample by gel filtration, In this subpopulation, the turnover number of the transport protein (the band 3 protein) for sulfate transport was determined. It was found that, in the reconstituted system, the protein transports sulfate 55lo-times faster than in the human erythrocyte membrane.Band 3 protein; Sulfate transport; Reconstitution; Turnover number: (Erythrocyte membrane)