Regarding the structure, CNNMs contain an N-terminal extracellular domain, a transmembrane domain called DUF21, a large cytosolic region that includes a pair of cystathionine-β-synthase domains, known as CBS-pair, and, furthermore, a putative cyclic nucleotide-binding homology domain, which name is CNBH (Cyclic Nucleotide-Binding Homology). The CBS-pair domain has been extensively characterized, yet little is known about the CNBH domain.
