(A) Topology of the 100–243 construct
of the KCNQ1 voltage-sensor
domain (Q1-VSD), which spans helices S0–S4, as inferred on
the basis of the results of this work. The sites for mutations linked
to long QT syndrome and related disorders are colored pink, while
sites for mutations linked to atrial fibrillation (AF) and related
disorders are colored yellow. (B) Sequence alignment (by ClusterW2)
of TM segments S2 and S4 of VSDs from various voltage-gated ion channels.
(C) Sodium dodecyl sulfate–polyacrylamide gel electrophoresis
gel stained with Coomassie blue, showing that purified Q1-VSD runs
as a monomer in SDS micelles, with an apparent molecular mass of 15
kDa.