Contributed Lecture
Activation of Divalent Transporter via Structure-Function Studies of Magnetosome-Associated Protein MamM and MamB

For navigation along the earth`s magnetic field magnetotactic bacteria form chains of magnetosomes, which are intracellular membrane-enclosed, nanometer-sized crystals of the magnetic iron mineral magnetite (Fe₃O₄). Biomineralization of magnetite within these unique prokaryotic organelles involves the uptake of large amounts of iron. In this work, we elucidated the structure-function relationships of MamM and MamB, which are suggested to be involved in iron transport during magnetite biomineralization and is prototypical members of the ubiquitous class of cation diffusion facilitators (CDF). We used a multi-faceted approach combining structural determination, biophysical characterizations, in vivo genetics and cellular imaging, to uncover the function(s) of MamM and MamB, and to elucidated the structural effects of mutations homologous to those which were identified to be human disease-associated in human CDF proteins. The combined use of microbiological, biochemical, and microscopic techniques helped to determine the functional importance of disease related key residues of human CDFs, mapped onto the C-terminal domain. These residues are also needed for MamM and MamB overall function in vivo. The results of our interdisciplinary and collaborative approach not only improved the understanding of magnetite biomineralization, but also yielded broader insights into how bacterial organelles are formed and contributed to a better functional understanding of the ubiquitous CDF protein family.