Elucidation of Mechanisms for Biomagnetite Formation and Its Application

本研究项目以磁性细菌Magnetoacellum magneticum AMB-1为研究对象，从基因组学、转录组学和蛋白质组学三个方面进行研究，以阐明生物磁铁矿合成的分子机制。最初，M. magneticum AMB-1被分析并发现由大小为4，967，148个碱基对的单个环状染色体组成。为了筛选出与生物磁铁矿形成相关的基因，基于磁性微囊藻AMB-1全基因组序列中注释的4492个基因设计了DNA微阵列，分析了铁诱导基因的全局基因表达。从全球基因表达谱，参与铁吸收系统和信号转导控制的开/关磁铁矿形成的基因进行了鉴定。M. magneticum AMB-1具有几个常见的铁摄取系统，但编码的基因调控是不寻常的。蛋白质组学分析，其中SDS-PAGE和2D-凝胶电泳图谱揭示了几个生物磁铁矿膜特异性蛋白质在生物磁性矿化中起着至关重要的作用。这些蛋白质被纯化并进一步表征。其中一个被鉴定的蛋白质与生物磁铁矿紧密结合，并在分离的蛋白质的存在下合成人工磁铁矿。还使用包括蛋白质的特定基序的肽进行人工形状控制的磁铁矿的生产。为了实现蛋白质在生物磁铁上的大量展示，优化了锚分子和启动子，并将多种功能蛋白质展示在生物磁铁上。在此基础上，我们成功地将七跨膜蛋白--G蛋白偶联受体（GPCRS）组装到生物磁铁矿上。

In this research project, we conducted research in genomics, transcriptomics and proteomics for the magnetic bacterium Magnetospirillum magneticum AMB-1 to clarify the molecular mechanism of biomagnetite synthesis. Initially, the whole genome sequence of M. magneticum AMB-1 was analyzed and was found to consist of a single circular chromosome of 4,967,148 base pairs in size. In order to identify the genes involved in biomagnetite formation, DNA microarray was designed based on 4492 genes annotated from the whole genome sequence of M magneticum AMB-1, and the global gene expression of iron inducible genes was analyzed. From the global gene expression profile, genes involved in iron uptake systems and signal transduction controlling the on/ off of magnetite formation were identified. M. magneticum AMB-1 possesses several iron uptake systems which are common but the encoded gene regulation is unusual. Proteomic analysis was also employed in which SDS-PAGE and 2D-gel electrophoresis profiles revealed several biomagnetite membrane-specific proteins which play crucial roles in biomagnetic mineralization. These proteins were purified and further characterized. One of the identified proteins tightly bound to the biomagnetite was produced, and artificial magnetite was synthesized in the presence of the isolated protein. Production of artificially shape-controlled magnetite was also conducted using peptides including specific motif of the protein. The elucidation of the mechanism of biomagnetite formation provides a roadmap for the design of novel nano-biomaterials useful in multidisciplinary fields.For large amount of protein display onto biomagnetite, anchor molecules and promoters were optimized, and several functional proteins were displayed onto biomagnetite. In the result, we have succeeded in assembling seven-transmembrane proteins, G protein coupled receptors (GPCRS) on biomagnetites.