Enables several functions, including calmodulin binding activity; protein kinase A binding activity; and voltage-gated potassium channel activity. Contributes to delayed rectifier potassium channel activity. Involved in several processes, including cellular response to cAMP; regulation of cardiac muscle cell membrane repolarization; and regulation of heart contraction. Located in several cellular components, including basolateral plasma membrane; endosome; and membrane raft. Part of voltage-gated potassium channel complex. Implicated in heart conduction disease (multiple); long QT syndrome (multiple); and type 2 diabetes mellitus. Biomarker of seminoma.