Impact of Mutations on the Structure of the Human Potassium Channel KCNQ1

Abstract

Approximately one in 2000 newborns are affected by congenital long QT syndrome (LQTS), which is a life-threatening cardiac disorder. Mutations in the voltage-gated potassium channel KCNQ1 and its accessory protein KCNE1 cause 50% of congenital LQTS. Up to now, more than 400 mutations have been identified in KCNQ1 from LQTS subjects. The mechanistic effects of many of these mutations remain unknown. In the present study, we have investigated the specific effects of 32 KCNQ1 mutations on the structural properties of isolated voltage-sensor domain of KCNQ1 using solution nuclear magnetic resonance spectroscopy. The 32 mutations are disease causing, benign, or of unknown significance. The high quality NMR spectra of wild type and of one engineered double mutation E160R-S225E serve as reference spectra, representing the open state (active conformation) and closed state (inactive conformation) forms of the channel, respectively. Mutants were labeled with 15N and purified into lysomyristoylphosphatidylglycerol (LMPG) detergent micelles. The 1H-15N TROSY-heteronuclear single quantum coherence spectroscopy spectrum of each mutant was collected and compared with the reference spectra. The effect of each mutation on the equilibrium between the channel active conformation and inactive conformation was determined. These results will advance our understanding of the molecular basis of LQTS pathogenesis and will be important for the rational design of anti-arrhythmia therapeutics for patients harboring KCNQ1 mutations.