The CCNM family proteins, also called ancient conserved domain proteins (ACDPs), are evolutionarily conserved Mg2+ transporters. CCNM, also called cyclin-Q (CCNQ), or CDK10-activating cyclin, or cyclin-related protein FAM58A, associates with CDK10 to promote its kinase activity. Members of this family contain two cyclin boxes. This model corresponds to the first one. The cyclin box is a protein binding domain.