ASSEMBLY OF MAMMALIAN VOLTAGE-GATED POTASSIUM CHANNELS - EVIDENCE FORAN IMPORTANT ROLE OF THE FIRST TRANSMEMBRANE SEGMENT

Three different experimental approaches were used to establish that th e first transmembrane segment (S1) is important for K+ channel assembl y. First, hydrodynamic analyses of in vitro translated Kv1.1 N-termina l domain containing the S1 segment coassembles to form hometetrameric complexes, whereas deletion of the S1 segment abolishes coassembly. Se cond, coimmunoprecipitation experiments of cotranslated Kv1.1 and Kv1. 5 truncated polypeptides show that the S1 segment is essential for coi mmunoprecipitation. Third, dominant negative experiments in Xenopus oo cytes confirm that overexpression of either the S1 segment or the N-te rminal domain is sufficient for abolishing the expression of functiona l Kv1.1 and Kv1.5 K+ channels. These data indicate that S1 segment pla ys an important role in the coassembly of homo- and heterotetrameric K + channels.