- Tetra-tricopeptide repeat (TPR) is a structural motif found as such or forming part of a bigger fold in a wide range of proteins. It serves as a template for protein-protein interactions and mediates multiprotein complexes . MamA is a unique, highly abundant, Magnetosome associated protein and predicted to contain 5 TPR motifs as well as predicted putative one. Magnetosome is a subcellular organelle that consists of a linear-chain assembly of inner membrane invaginations each able to biomineralize and enclose a ~50-nm crystal of magnetite or greigite. Magnetosome allows magnetotactic bacteria, a diverse group of aquatic microorganisms, to orientate themselves along geomagnetic fields in search of suitable environments . MamA is one of the most characterized magnetosome-associated proteins in vivo and yet, its function is not clear [3-5]. Here, we report on the crystallization and structure analysis of recombinant M. magneticum (AMB-1) and M. gryphiswaldense (MSR-1) MamA deletion mutants. The structures were determined to a resolution of 2.0 Å and confirmed MamA fold as a five TPR motifs containing protein.