STRUCTURE-ACTIVITY-RELATIONSHIPS OF THE K-V-BETA-1 INACTIVATION DOMAIN AND ITS PUTATIVE RECEPTOR PROBED USING PEPTIDE ANALOGS OF VOLTAGE-GATED POTASSIUM CHANNEL ALPHA-SUBUNIT AND BETA-SUBUNIT

Certain beta-subunits exert profound effects on the kinetics of voltag e-gated (K-v) potassium channel inactivation through an interaction be tween the amino-terminal ''inactivation domain'' of the beta-subunit a nd a ''receptor'' located at or near the cytoplasmic mouth of the chan nel pore. Here we used a bacterial random peptide library to examine t he 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 a lpha-subunit (residues 313-328), Among the highest affinity interactor s were peptides with significant homology to the amino terminus of K(v )beta 1. We performed a second screen using a peptide from the amino t erminus of K(v)beta 1 (residues 2-31) as ''bait'' and identified pepti de sequences with significant homology to the 54-55 loop of K(v)1.1. A series of synthetic peptides containing mutations of the wild-type K( v)beta 1 and K(v)1.1 sequences were examined for their ability to inhi bit Kv beta 1/K(v)1.1 binding. Amino acids Arg(20) and Leu(21) in K(v) beta 1 and residues Arg(324) and Leu(328) in K(v)1.1 were found to be important for the interaction. Taken together, these data provide supp ort for the contention that the 54-55 loop of the K(v)1.1 alpha subuni t is the likely acceptor for the Kv beta 1 inactivation domain and pro vide information about residues that may underlie the protein-protein interactions responsible for beta-subunit mediated K-v channel inactiv ation.