Cyclin M2, also known as CNNM2 or ACDP2 (ancient conserved domain-containing protein 2), is an 875 amino acid multi-pass membrane protein that contains two CBS domains and belongs to the ACDP family. Expressed in a variety of tissues with highest expression in placenta, brain and kidney, cyclin M2 functions as a divalent metal cation transporter that mediates the transport of several different metal cations, including Mg2+, Co2+ and Fe2+. Cyclin M2 exists as multiple alternatively spliced is