趋磁性细菌利用一种被称为“磁小体”的专门化细胞器（磁铁矿(Fe(II)Fe(III)2O4)或硫复铁矿(Fe(II)Fe(III)2S4)的一种生物矿化晶体）来探测地球磁场，并与其方向保持一致。
这篇论文介绍了与“磁小体”相结合的蛋白MamP的X-射线晶体结构，它显示了由融合到两个“磁小体”域上的一个“自插入”（self-plugged）PDZ域构成的一个独特排列。
作者还确定，MamP是一个铁氧化酶，有助于“三价铁”水铁矿的形成，因此对于在“磁小体”生物生成过程中的铁管理机制很重要。（生物谷Bioon.com)
生物谷推荐的英文摘要
Nature doi:10.1038/nature12573
Structural insight into magnetochrome-mediated magnetite biomineralization
Marina I. Siponen，Pierre Legrand，Marc Widdrat，Stephanie R. Jones，Wei-Jia Zhang，Michelle C. Y. Chang，Damien Faivre，Pascal Arnoux& David Pignol
Magnetotactic bacteria align along the Earth’s magnetic field using an organelle called the magnetosome， a biomineralized magnetite (Fe(ii)Fe(iii)2O4) or greigite (Fe(ii)Fe(iii)2S4) crystal embedded in a lipid vesicle. Although the need for both iron(ii) and iron(iii) is clear， little is known about the biological mechanisms controlling their ratio1. Here we present the structure of the magnetosome-associated protein MamP and find that it is built on a unique arrangement of a self-plugged PDZ domain fused to two magnetochrome domains， defining a new class of c-type cytochrome exclusively found in magnetotactic bacteria. Mutational analysis， enzyme kinetics， co-crystallization with iron(ii) and an in vitro MamP-assisted magnetite production assay establish MamP as an iron oxidase that contributes to the formation of iron(iii) ferrihydrite eventually required for magnetite crystal growth in vivo. These results demonstrate the molecular mechanisms of iron management taking place inside the magnetosome and highlight the role of magnetochrome in iron biomineralization.
