Structure-activity relationships of the K(v)β1 inactivation domain and its putative receptor probed using peptide analogs of voltage-gated potassium channel α- and β-subunits

Abstract

Certain β-subunits exert profound effects on the kinetics of voltage- gated (K(v)) potassium channel inactivation through an interaction between the amino-terminal 'inactivation domain' of the β-subunit and a 'receptor' located at or near the cytoplasmic mouth of the channel pore. Here we used a bacterial random peptide library to examine the structural requirements for this interaction. To identify peptides that bind K(v)1.1 we screened the library against a synthetic peptide corresponding to the predicted S4-S5 cytoplasmic loop of the K(v)1.1 α-subunit (residues 313-328). Among the highest affinity interactors were peptides with significant homology to the amino terminus of K(v)β1. We performed a second screen using a peptide from the amino terminus of K(v)β1 (residues 2-31) as 'bait' and identified peptide sequences with significant homology to the S4-S5 loop of K(v)1.1. A series of synthetic peptides containing mutations of the wild-type K(v)β1 and K(v)1.1 sequences were examined for their ability to inhibit K(v)β1/K(v)1.1 binding. Amino acids Arg20 and Leu21 in K(v)β1 and residues Arg234 and Leu328 in K(v)1.1 were found to be important for the interaction. Taken together, these data provide support for the contention that the S4-S5 loop of the K(v)1.1 α subunit is the likely acceptor for the K(v)β1 inactivation domain and provide information about residues that may underlie the protein-protein interactions responsible for β-subunit mediated K(v) channel inactivation.