Potassium channel regulatory subunit that modulate the delayed rectifier voltage-gated potassium channel activity of KCNB1 and KCNB2 by altering their kinetics, expression levels, and shifting the half-inactivation potential to more polarized values (PubMed:10484328). While it does not form functional channels on its own, it can form functional heterotetrameric channels with KCNB1 and KCNB2 (PubMed:10484328). Each regulatory subunit has unique regulatory properties that can lead to extensive inhibition, significant changes in kinetics, and/or substantial shifts in the voltage dependencies of the inactivation process (By similarity). . This is the function of Ensembl gene identifier ENSG00000124134 (KCNS1, potassium voltage-gated channel modifier subfamily S member 1).