Magnetochrome: a c-type cytochrome domain specific to magnetotatic bacteria

• DOI: 10.1042/bst20120104
• Publication Date: 2012-11-23T17:09:55Z
• Authors: Marina I. Siponen; Géraldine Adryanczyk; Nicolas Ginet; Pascal Arnoux; David Pignol
• Keywords: Magnetosome; Magnetotactic Bacteria; Greigite; Organelle

Magnetotactic bacteria consist of a group taxonomically, physiologically and morphologically diverse prokaryotes, with the singular ability to align geomagnetic field lines, phenomenon referred as magnetotaxis. This magnetotactic property is due presence iron-rich crystals embedded in lipidic vesicles forming an organelle called magnetosome. Magnetosomes are composed single-magnetic-domain nanocrystals magnetite (Fe3O4) or greigite (Fe3S4) biological membranes, thereby prokaryotic organelle. Four specific steps described this formation: (i) membrane specialization, (ii) iron acquisition, (iii) (or greigite) biocrystallization, (iv) magnetosome alignment. The formation these magnetic genetically controlled process, which governed by enzyme-catalysed processes. On basis protein sequence analysis genes known be involved Magnetospirillum magneticum AMB-1, we have identified subset three membrane-associated periplasmic proteins containing double cytochrome c signature motif CXXCH: MamE, MamP MamT. suggests existence electron-transport chain inside magnetosome, contributing process biocrystallization. We performed heterologous expression E. coli motif-containing domains Initial biophysical characterization has confirmed that MamT indeed c-type cytochromes. Furthermore, determination redox potentials for new family cytochromes reveals midpoint −76 −32 mV MamE respectively.