TOM complex proteins that primarily function in mitochondrial import also have moonlighting roles in the formation and maintenance of mitochondria contact sites. Tom40, for example, acts as the mitochondrial receptor in the yeast vacuole-mitochondria contact site (vCLAMP). Tom40 also localizes to ER-mitochondria contact sites in mammalian cells and facilitates the import of NDUFS4, a respiratory complex component. Another mitochondrial import protein, Tom70, is found at ER-mitochondria contact sites in both yeast and mammalian cells and is implicated in calcium transfer in the latter cell type.