CL- CHANNELS IN BASOLATERAL RENAL MEDULLARY VESICLES .VIII. PARTIAL-PURIFICATION AND FUNCTIONAL RECONSTITUTION OF BASOLATERAL MTAL CL- CHANNELS

Cl- channels fused from basolateral mTAL membranes into planar bilayer s have distinctive functional characteristics which, when taken togeth er, are unique among Cl- channels. The properties of these 50 to 60 pS channels can account for the characteristics of basolateral Cl- condu ctances in microperfused mTAL segments and thus may mediate net basola teral Cl- absorption in the intact mTAL. In the present studies, we so lubilized basolateral membranes from rabbit mTAL. Since basolateral mT AL Cl- channels contain arginine- and lysine-rich domains, we exposed these solubilized membranes to sequential cation- and anion-exchange c hromatography. The bound and unbound eluates from cation- and anion-ex change chromatography were reconstituted into proteoliposomes which, w hen fused into bilayers, yielded Cl- channels whose properties were vi rtually identical to those described above for native basolateral mTAL channels fused into bilayers. As judged by valinomycin-sensitive cond uctive Cl-36(-) uptake, proteoliposomes reconstituted from the unbound eluates after anion-exchange chromatography were enriched at least 30 -fold in Cl- channel activity and had about 30% of the total Cl- chann el activity solubilized in native vesicles.