FXYD domain-containing ion transport regulator 3 and similar proteinsThis subfamily includes FXYD domain-containing ion transport regulator 3 (FXYD3), FXYD9, and FXYD10, also called PLMS/Phospholemman-like protein. FXYD3, also known as mammary tumor 8 kDa protein (MAT-8), or chloride conductance inducer protein Mat-8, or phospholemman-like (PLML), may function as a chloride channel or as a chloride channel regulator. It associates with and regulates the activity of the sodium/potassium-transporting ATPase (NKA) which transports Na+ out of the cell and K+ into the cell. Two transcript variants encode two different isoforms of the protein; in addition, transcripts utilizing alternative polyA signals have been described in the literature. Members here include mammalians and reptiles. FXYD9 is present in teleosts including: Danio rerio, Atlantic salmon, and Japanese Medaka fish. In general, the FXYD9 isoform has the highest degree of conservation among the examined teleost species, indicating that it may be involved in physiological processes that are not evolving within this group of vertebrates. FXYD10, present in shark, associates with and modifies the activity of Na,K-ATPase in vitro through interactions mediated by its transmembrane and cytoplasmic C-terminal domains. It is important in the phosphorylation and potassium deocclusion reactions, which are known to be controlled by A domain movements. It is thought that FXYD10 interacts with the A domain of the shark Na,K-ATPase alpha-subunit.