CATION SELECTIVITY OF CHANNELS FORMED AT PLANAR LIPID BILAYER BY PINELLIA-TERNATA LECTIN

By means of the two-compartment system, PTL-channels, the first lectin channels formed on planar lipid bilayers by Pinellia ternata lectin ( PTL) have been studied. The results show (i) PTL-channels are voltage- independent and have apparent subunits; (ii) in 50 mmol/L KCl and 25 m mol/L BaCl2 solutions a single channel has unit conductance of 21 pS a nd 42 pS, respectively; (iii) the channel exhibits a slightly higher p ermeability to divalent than monovalent cation (P(Ba)/P(K) = 4. 1), an d (iv) the selectivity among divalent or monovalent cations is poor. T he cation selectivity sequence for the channel Will follow P(Ba) (7.0) is similar to P(Sr) (6.4) is similar to P(Mg)(6.4)>P(K)(1.7)>P(Na)(1. 0)is similar to P(Li)(1.0). Moreover, these data also give explanation to the facilitatory action of PTL on the release of acetyl-choline fr om motor nerve terminals.