Interaction sites between the Slo1 pore and the NH2 terminus of the β2 subunit, probed with a three-residue sensor

Abstract

Calcium- and voltage-gated (BK) K+ channels encoded by Slo1 play an essential role in nervous systems. Although it shares many common features with voltage-dependent KV channels, the BK channel exhibits differences in gating and inactivation. Using a mutant in which FWI replaces three residues (FIW) in the NH2 terminus of wild-type β2-subunits, in conjunction with alanine-scanning mutagenesis of the Slo1 S6 segment, we identify that the NH2 terminus of β2-subunits interacts with the residues near the cytosolic superficial mouth of BK channels during inactivation. The cytosolic blockers did not share the sites with NH 2 terminus of β2-subunits. A novel blocking-inactivating scheme was proposed to account for the observed noncompetition inactivation. Our results also suggest that the residue Ile-323 plays a dual role in interacting with the NH2 terminus of β2-subunits and modulating the gating of BK channels. © 2007 by The American Society for Biochemistry and Molecular Biology, Inc.