Formation of Cation Channels

Concomitant with translocation, cation channels are formed in the membrane (Sandvig and Olsnes, 1988 Papini et al., 1988) which are selective for monovalent cations. Small ions penetrate more easily 

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Falnes P0, Madshus IH, Sandvig K, Olsnes S (1992) Replacement of negative by positive charges in the presumed membrane-inserted part of diphtheria toxin B-fragment. Effect on membrane translocation and formation of cation channels. J Biol Chem 267 12284-12290. 

Venturiddin, a highly specific blocker, decreased the channel open probability significantly (Hg.2). Therefore it was likely, that the described cation channels did not arise from contaminations in purified CF CF. Compared to the intact ATP- thase, vdiere 0.5 p.M Venturiddin completely abolish ATP synthesis, the K seemed to be higher. Venturiddin is assumed to bind to subunit m of the channel portion of the AlT-synthase (14). In ei riments with purified subunit m of CF (Fi 5) cation channels with conductance states and gating behaviour similar to CF CF were <%served. These results implied that subunit HI (liberated from CF CF -complexes) was responsible for the formation of cation channels. 

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