[Isoform 1]: Mediates the voltage-dependent potassium ion permeability of excitable membranes. Assuming opened or closed conformations in response to the voltage difference across the membrane, the protein forms a potassium-selective channel through which potassium ions may pass in accordance with their electrochemical gradient. . [Isoform 2]: Mediates the voltage-dependent potassium ion permeability of excitable membranes. Assuming opened or closed conformations in response to the voltage difference across the membrane, the protein forms a potassium-selective channel through which potassium ions may pass in accordance with their electrochemical gradient. {ECO:0000269|PubMed:1373731, ECO:0000269|PubMed:1547020, ECO:0000269|PubMed:1986382, ECO:0000269|PubMed:36852591}. [Isoform 3]: Lacks voltage-gated potassium channel activity. . This is the function of KCNA3 (potassium voltage-gated channel subfamily A member 3, ENSG00000177272).