Carboxy‐terminal domain mediates assembly of the voltage‐gated rat ether‐à‐go‐go potassium channel

The specific assembly of subunits to oligomers is an important prerequisite for producing functional potassium channels. We have studied the assembly of voltage‐gated rat ether‐à‐go‐go (r‐eag) potassium channels with two complementary assays. In protein overlay binding experiments it was shown that a 41‐amino‐acid domain, close to the r‐eag subunit carboxy‐terminus, is important for r‐eag subunit interaction. In an in vitro expression system it was demonstrated that r‐eag subunits lacking this assembly domain cannot form functional potassium channels. Also, a ∼10‐fold molar excess of the r‐eag carboxy‐terminus inhibited in co‐expression experiments the formation of functional r‐eag channels. When the r‐eag carboxy‐terminal assembly domain had been mutated, the dominant‐negative effect of the r‐eag carboxy‐terminus on r‐eag channel expression was abolished. The results demonstrate that a carboxy‐terminal assembly domain is essential for functional r‐eag potassium channel expression, in contrast to the one of Shaker‐related potassium channels, which is directed by an amino‐terminal assembly domain.