2.A.4.7.4
Putative magnetosome membrane iron transporter, MamM.  Forms a heterodimeric stable complex with MamB which it stabilizes.  MamB (see TC# 2.A.4.7.3) also interacts with other proteins including the PDZ1 domain of MamE (Q6NE61).  Both MamB and MamM are essential for magnetite biomineralization and are involved in several steps in magnetosome formation, but only MamB is essential for formation of magnetosome membrane vesicles (Uebe et al. 2011). Most CDF proteins contain two domains, the cation transporting transmembrane domain and the regulatory cytoplasmic C-terminal domain (CTD). A MamM M250P mutation that is synonymous with the disease-related mutation L349P of the human CDF protein, ZnT-10 causes severe structural changes in its CTD, resulting in abnormally reduced function.Thus, the CTD fold is critical for the CDF proteins' proper function and suggest that the CDF cytoplasmic domain is a CDF regulatory element (Barber-Zucker et al. 2016). MamM's CTD can discriminate against Mn²⁺, supporting its postulated role in preventing magnetite formation poisoning in magnetotactic bacteria via Mn²⁺ incorporation (Barber-Zucker et al. 2020).