Elucidation of Mechanisms for Biomagnetite Formation and Its Application

本研究对磁性磁螺菌AMB-1进行了基因组学、转录组学和蛋白质组学等方面的研究，以阐明生物磁铁矿合成的分子机制。首先对磁链霉菌AMB-1的全基因组序列进行了分析，发现AMB-1由一个4967,148个碱基对的单环染色体组成。为了确定与生物磁铁矿形成有关的基因，设计了基于磁链霉菌AMB-1全基因组序列4492个基因注释的DNA微阵列，并分析了铁诱导基因的整体表达。从全球基因表达谱中，鉴定了与铁吸收系统和信号转导有关的基因，这些基因控制着磁铁矿形成的开关。磁链霉菌AMB-1具有几个常见的铁摄取系统，但编码的基因调控不寻常。蛋白质组学分析表明，在生物磁性成矿过程中，有几种生物磁云膜特有的蛋白质在生物磁化过程中起着关键作用。对这些蛋白进行了纯化，并对其进行了鉴定。产生了与生物磁铁矿紧密结合的一种鉴定蛋白质，并在分离的蛋白质存在下合成了人造磁铁矿。还利用含有特定蛋白质基序的多肽进行了人工形状控制磁铁矿的生产。生物磁铁矿形成机理的阐明为新型纳米生物材料在多学科领域的应用设计提供了路线图。为了在生物磁铁矿上展示大量的蛋白质，优化了锚定分子和启动子，并将几种功能蛋白质展示在生物磁铁矿上。结果，我们成功地组装了七种跨膜蛋白，即生物磁石上的G蛋白偶联受体(GPCRs)。

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.