The magnetosome is a subcellular organelle in magnetotactic bacteria that consists of a linear-chain assembly of lipid vesicles. Each magnetosome is able to biomineralize and enclose a ~50-nm crystal of magnetite or greigite. MamB is abundant magnetosomal membrane protein that share similarity to cation diffusion facilitator (CDF) protein family. MamB is a multifunctional protein that was shown to be essential for iron transport and magnetosome membrane formation. Recent studies have demonstrated that deletion of MamB leads to the abolishment of the magnetosome. To understand the differences between MamB and other CDFs we started a structural work using X-ray crystallography. Here we present the crystallization and the structure of the MamB cytosolic domain from Marine magnetic spirillum QH-2 and Candidatus Desulfamplus magnetomortis BW-1 Greigite forming protein. Additionally, we were able to obtain a zinc bound state for QH-2 MamB that allowed us to locate the iron binding sites. Together these results shed light on the structure conservation of CDFs while pointing on unique divalent binding sites.
