Functional significance of rSK2 N-terminal region revealed by electrophysiology and Preliminary Structural Studies

Small conductance calcium-activated potassium channels (or SKCa channels) are potassium selective, voltage-independent, and activated by intracellular calcium concentration. These channels play important roles in excitable cells such as neuron in the central nervous system (Vergara et al., 1998). The activity of SKCa channels underlies the slow afterhyperpolarization that inhibits neuronal cell firing (Hille, 1991; Vergara et al.,1998). Until now, N-terminal region of rSK2 isn't characterized. To study the role of N-terminus, we constructed the N-terminal deletion mutant and characterized by electrophysiological means. Interestingly, N-terminal deletion mutant be trafficked to membrane couldn't evoke any ionic currents. Thus, N-terminal region has a role in functional rSK2 channel formation. To elucidate the function of N-terminal region, (His)6-conjugated protein was purified and filtrated by affinity column chromatography. Surprisingly, N-terminal region was shown in tetramer size that was supported by cross-linking result. Thus, we predicted that N-terminal region might be involved in the tetramerization of rSK2.