(A) Sequence alignment of KCNE1 cytoplasmic domains with C-termini of the other KCNE family members. (B) Alignments of the partial amino acid sequences of KCNQ1 C-terminal region containing helix A compared to other KCNQ family members. (C) Schematic representation of recombinant constructs use in this study. Q1Cf refers to the full-length KCNQ1-C-terminus and Q1C1, Q1C2, Q1C3, Q1C1A, Q1C1B each refer to truncated Versions as illustrated. E1C refers to the KCNE1-C-terminus. Boldface residues are those subjected to mutagenesis. All recombinant proteins were expressed in E. coli BL21 (DE3) pLsS strains, and purified with a Ni-affinity column followed by Superdex 200 gel filtration chromatography. (Numbers indicate amino acid position; black and shaded boxes represent α-helical segments)