Probing the Protein-Protein Interactions between KCNQ1 and KCNE1 using Electron Paramagnetic Resonance (EPR) Spectroscopy

Abstract

KCNQ1 is a membrane-bound protein composed of 676 amino acids with a molecular weight of 75 kD and contains 6 transmembrane helices. KCNQ1 is a voltage-gated potassium channel primarily involved in the transport of potassium in the human heart. The activity of KCNQ1 is modulated by the integral membrane protein KNCE1 (also known as MinK). This potassium modulation is critical for repolarization in the heart, specifically in the left ventricle. Mutations in the KCNQ1 and KCNE1 genes have been linked to genetic disorders such as long QT syndrome, sudden infant death syndrome (SIDS), as well as deafness. However, most current studies between KNCQ1 and KCNE1 have been from an electrophysiological or functional standpoint, which leaves structural and dynamic information on the proteins unknown. EPR spectroscopy is a powerful structural biology tool that can be used to probe both protein structures as well as protein-protein interactions between KCNQ1 and KCNE1. Currently, we have overexpressed full length KCNE1 and the C-terminal domain of KCNQ1. In this study, we used both continuous-wave (CW) EPR and the pulsed EPR technique of double electron-electron resonance (DEER) to probe the structural and dynamic parameters of the interaction of KCNQ1 and KCNE1.