The function of FXYD6 (FXYD domain containing ion transport regulator 6, Ensembl gene identifier ENSG00000137726) is as follows. Associates with and regulates the activity of the sodium/potassium-transporting ATPase (NKA) which catalyzes the hydrolysis of ATP coupled with the exchange of Na(+) and K(+) ions across the plasma membrane. Reduces the apparent affinity for intracellular Na(+) with no change in the apparent affinity for extracellular K(+) (PubMed:33231612). In addition to modulating NKA kinetics, may also function as a regulator of NKA localization to the plasma membrane (By similarity). {ECO:0000250|UniProtKB:Q91XV6, ECO:0000269|PubMed:33231612}.