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Ca2+ activation of hSlo K+ channel is suppressed by N-terminal GFP tag
1Department of Membrane and Neurophysics, Max-Planck-Institute for Biochemistry, D-82152 Martinsride/München, Germany.
Abstract:
The human slow poke (hSlo) K+ channel was tagged with GFP (green fluorescent protein) at the N-terminus of its alpha-subunit. The fusion protein was expressed transiently in HEK293 cells; it formed functional voltage-gated channels as shown by whole cell patch-clamp measurements. However, the tag lowered the voltage dependence of gating and it suppressed the typical left-shift of gating by intracellular binding of Ca2+. The location of the GFP-tagged N-terminus was confirmed to be on the extracellular side by application of a monoclonal antibody to nonpermeabilized cells. Structural interpretations of the effects are discussed.