Centrin 4 is a Binding Partner of Rat EAG1 K+ Channels
The ether a go go (Eag) potassium (K+ channel belongs to the superfamily of voltage gated K+ channel. In mammals, the expression of Eag channels is neuron specific but their neurophysiological role remains obscure. We have applied the yeast two hybrid screening system to identify rat Eag1 (rEag1) interacting proteins from a rat brain cDNA library. One of the clones we identified was centrin 4, which is an EF hand calcium binding protein with four putative calciumion binding sites. Data from in vitro yeast two hybrid and GST pull down assays suggested that the direct association with centrin was mediated by the carboxyl termini of rEag1. Co precipitation of the two proteins was confirmed in both heterologous HEK293T cells and brain lysates. Centrin 4 and calmodulin are closely related four EF hand calcium binding proteins. The binding affinity of calmodulin to rEag1 was notably enhanced in the presence of calcium. In contrast, the interaction between centrin 4 and rEag1 appeared to be calcium independent. We therefore propose that centrin 4 may serve as a constitutive binding partner of rEag1.