title: Genetic and biochemical investigations of the role of MamP in redox control of iron biomineralization in Magnetospirillum magneticum.
abstract: Magnetotactic bacteria have evolved complex subcellular machinery to construct linear chains of magnetite nanocrystals that allow the host cell to sense direction. Each mixed-valent iron nanoparticle is mineralized from soluble iron within a membrane-encapsulated vesicle termed the magnetosome, which serves as a specialized compartment that regulates the iron, redox, and pH environment of the growing mineral. To dissect the biological components that control this process, we have carried out a genetic and biochemical study of proteins proposed to function in iron mineralization. In this study, we show that the redox sites of c-type cytochromes of the Magnetospirillum magneticum AMB-1 magnetosome island, MamP and MamT, are essential to their physiological function and that ablation of one or both heme motifs leads to loss of function, suggesting that their ability to carry out redox chemistry in vivo is important. We also develop a method to heterologously express fully heme-loaded MamP from AMB-1 for in vitro biochemical studies, which show that its Fe(III)-Fe(II) redox couple is set at an unusual potential (-89 ± 11 mV) compared with other related cytochromes involved in iron reduction or oxidation. Despite its low reduction potential, it remains competent to oxidize Fe(II) to Fe(III) and mineralize iron to produce mixed-valent iron oxides. Finally, in vitro mineralization experiments suggest that Mms mineral-templating peptides from AMB-1 can modulate the iron redox chemistry of MamP.
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720-1460;
authors.forename: Stephanie R
authors.initials: SR
authors.lastname: Jones
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720-1460;
authors.forename: Tiffany D
authors.initials: TD
authors.lastname: Wilson
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720-1460;
authors.forename: Margaret E
authors.initials: ME
authors.lastname: Brown
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102;
authors.forename: Lilah
authors.initials: L
authors.lastname: Rahn-Lee
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720-1460;
authors.forename: Yi
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720-1460;
authors.forename: Laura L
authors.initials: LL
authors.lastname: Fredriksen
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102;
authors.forename: Ertan
authors.initials: E
authors.lastname: Ozyamak
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102; Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200; and.
authors.forename: Arash
authors.initials: A
authors.lastname: Komeili
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720-1460; Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200; and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 mcchang@berkeley.edu.
authors.forename: Michelle C Y
authors.initials: MC
authors.lastname: Chang
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D001696:Biomechanical Phenomena; D003580:Cytochromes / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry; D006418:Heme / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007477:Ions; D007501:Iron / Q000737:chemistry; D055944:Magnetosomes / Q000378:metabolism*; D042201:Magnetospirillum / Q000378:metabolism*; D053768:Metal Nanoparticles / Q000737:chemistry; D008670:Metals / Q000737:chemistry; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D012995:Solubility
chemical_list: D001426:Bacterial Proteins; D003580:Cytochromes; D005290:Ferric Compounds; D007477:Ions; D008670:Metals; D010455:Peptides; C000499:ferric oxide; D006418:Heme; D007501:Iron; D010100:Oxygen
keywords: MamP; biomineralization; cytochrome; iron; magnetosome