期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：13
页码：3904-3909
DOI：10.1073/pnas.1417614112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceBiomineralization is an important and widespread phenomenon by which living systems produce solid materials from soluble metal ions and has key implications with regard to environmental and health processes. In this work, we report studies of redox and structural components that control mineralization events in the production of iron nanoparticles in directional-sensing bacteria. 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.
关键词：biomineralization ; iron ; magnetosome ; cytochrome ; MamP
