A STUDY OF RECONSTITUTED ANION CHANNELS USING LIPID BILAYERS

A chloride channel from impermeant sarcoplasmic reticulum (SR) was emb edded in a planar lipid bilayer (BLM) and its electrical properties de termined. Studies using ER-derived vesicles fused with BLMs have shown that they are permeable to Na+, K+, choline and Cl- but less permeabl e to Ca2+ and Mg2+. Though highly permeable to K+, the liver ER membra ne has been postulated to a lack of an efficient ion-conducting struct ure for K+ channel in the SR. The present study was undertaken with th e aim to look at the anionic, Ca2+ and K+ permeability pathways presen t in the ER membrane. Our reconstituted system exhibits considerable a nionic permeability following the sequence: SCN- > I- > Br-Cl- > gluco nate. The findings suggest the chloride channels have low field-streng th sites. It can be pharmacologically dissected to Zn2+-sensitive and DIDS-sensitive types. The gating of the channel is weakly voltage-depe ndent and at higher positive or negative voltages the channel prefers the low sub-conductance states. (C) 1998 Elsevier Science S.A.