Activity of Potassium Channel BmK-NSPK Inhibitor Regulated by Basic Amino Acid Residues: Novel Insight into the Diverse Peptide Pharmacology

The molecular interactions between venomous peptides and potassium channels have extensively enriched the knowledge of diverse peptide pharmacology, and the in-depth understanding of general features of the various peptide functions remains a formidable challenge. In this work, the role of peptide basic residues in peptide pharmacology was first investigated. Although the venomous BmK-NSPK peptide had the critically conserved functional residues occurring in its similar and potent potassium channel-inhibiting peptides, it was a remarkably weak inhibitor of potassium channels due to fewer basic residues. Additionally, 1 μM BmK-NSPK only inhibited 1.2 ± 1.0%, 1.7 ± 0.70%, 2.3 ± 0.49% and 5.4 ± 0.70% of hKv1.1, hKv1.2, hKv1.3 and hKv1.6 channel currents. The introduction of one or two basic residues in BmK-NSPK-I15K, BmK-NSPK-I18K, BmK-NSPK-I26K and BmK-NSPK-I18K/I26K could not improve BmK-NSPK activity. The modifications of more than three basic residues were found to continuously improve BmK-NSPK activity, and the corresponding BmK-NSPK-7K and BmK-NSPK-8K mutants could effectively inhibit hKv1.3 channel with IC50 values of 2.04 ± 0.68 nM and 21.5 ± 1.99 nM, respectively. Also, 1 μM BmK-NSPK-7K and BmK-NSPK-8K mutants could inhibit 84.1 ± 7.0% and 84.3 ± 1.8% of hKv1.1 channel currents. In addition, BmK-NSPK-7K and BmK-NSPK-8K mutants were found to differentially inhibit hKv1.6 and chimeric hKv1.3 channels. These findings first highlight the critical role of basic residues in the activity of potassium channel peptide inhibitors and provide novel insight into the diverse peptide pharmacology.