IS3 peptide-formed ion channels in rat skeletal muscle cell membranes

A 22-mer peptide, identical to the primary sequence of domain I segment 3 ( IS3) of rat brain sodium channel I, was synthesized. With the patch clamp c ell-attached technique, single channel currents could be recorded from the patches of cultured rat myotube membranes when the patches mere held at hyp erpolarized potentials and the electrode solution contained NaCl and 1 mu M IS3, indicating that IS3 incorporated into the membranes and formed ion ch annels, The single channel conductances of IS3 channels were distributed he terogeneously, but mainly in the range of 10-25 pS, There was a tendency th at the mean open time and open probability of IS3 channels increased and th e mean close time decreased,vith the increasing of hyperpolarized membrane potentials, IS3 channels are highly selective for Na+ and Li+ but not for C l- and K+, similar to the authentic Na+ channels. (C) 1999 Federation of Eu ropean Biochemical Societies.