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The cation diffusion facilitator proteins MamB and MamM of Magnetospirillum gryphiswaldense have distinct and complex functions, and are involved in magnetite biomineralization and magnetosome membrane assembly
Author(s) -
Uebe René,
Junge Katja,
Henn Verena,
Poxleitner Gabriele,
Katzmann Emanuel,
Plitzko Jürgen M.,
Zarivach Raz,
Kasama Takeshi,
Wanner Gerhard,
Pósfai Mihály,
Böttger Lars,
Matzanke Berthold,
Schüler Dirk
Publication year - 2011
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2011.07863.x
Subject(s) - magnetosome , magnetotactic bacteria , biomineralization , major facilitator superfamily , magnetite , greigite , bacterial outer membrane , biophysics , biology , organelle , chemistry , biochemistry , mutant , gene , escherichia coli , astrobiology , paleontology
Summary Magnetotactic bacteria form chains of intracellular membrane‐enclosed, nanometre‐sized magnetite crystals for navigation along the earth's magnetic field. The assembly of these prokaryotic organelles requires several specific polypeptides. Among the most abundant proteins associated with the magnetosome membrane of Magnetospirillum gryphiswaldense are MamB and MamM, which were implicated in magnetosomal iron transport because of their similarity to the cation diffusion facilitator family. Here we demonstrate that MamB and MamM are multifunctional proteins involved in several steps of magnetosome formation. Whereas both proteins were essential for magnetite biomineralization, only deletion of mamB resulted in loss of magnetosome membrane vesicles. MamB stability depended on the presence of MamM by formation of a heterodimer complex. In addition, MamB was found to interact with several other proteins including the PDZ1 domain of MamE. Whereas any genetic modification of MamB resulted in loss of function, site‐specific mutagenesis within MamM lead to increased formation of polycrystalline magnetite particles. A single amino acid substitution within MamM resulted in crystals consisting of haematite, which coexisted with magnetite crystals. Together our data indicate that MamM and MamB have complex functions, and are involved in the control of different key steps of magnetosome formation, which are linked by their direct interaction.