Magnetotactic bacterium, Magnetospirillum magneticum, produces biogenic magnetic nanoparticles termed magnetosomes, which are primarily composed of a magnetite core and a surrounding lipid bilayer membrane. We have fabricated human transmembrane protein-magnetosome complexes by genetic engineering with embedding the transmembrane proteins of interest, in particular G protein-coupled receptors (GPCRs), in the magnetosome membrane. The magnetosomes provide a promising platform for high throughput ligand screening towards drug discovery, and this is a critical advantage of the magnetosome display system beyond conventional membrane platforms such as liposomes and lipid nano-discs. However, the human GPCRs expressed on the magnetosomes were not fully functionalized in bacterial membranes the most probably due to the lack of essential phospholipids such as phosphatidylcholine (PC) for GPCR functionalization. To overcome this issue, we expressed two types of PC-producing enzymes, phosphatidylcholine synthase (PCS) and phosphatidylethanolamine N-methyltransferase (PMT) in M. magneticum. As a result, generation and incorporation of PC in cell- and magnetosome-membranes were demonstrated. To the best of our knowledge, M. magneticum is the second bacterial species which had the PC-incorporated lipid membrane by genetic engineering. Subsequently, a GPCR, thyroid-stimulating hormone receptor (TSHR) and PCS were simultaneously expressed. We found that PC in the magnetosome membrane assisted the binding of TSHR and its ligand, indicating that the genetic approach demonstrated in this study is useful to enhance the function of the GPCRs displayed on the magnetosomes.

趋磁细菌，Magnetospirillum magneticum，产生称为磁小体的生物磁性纳米颗粒，其主要由磁铁矿核心和周围的脂质双层膜组成。我们通过基因工程制造了人类跨膜蛋白-磁小体复合物，将感兴趣的跨膜蛋白，特别是 G 蛋白偶联受体 (GPCR) 嵌入磁小体膜中。磁小体为药物发现的高通量配体筛选提供了一个有前景的平台，这是磁小体展示系统超越脂质体和脂质纳米盘等传统膜平台的关键优势。然而，磁小体上表达的人类 GPCR 在细菌膜中没有完全功能化，这很可能是由于缺乏用于 GPCR 功能化的必需磷脂如磷脂酰胆碱 (PC)。为了克服这个问题，我们表达了两种类型的 PC 生成酶，磷脂酰胆碱合酶 (PCS) 和磷脂酰乙醇胺磁性分枝杆菌中的N-甲基转移酶 (PMT) 。结果，证明了 PC 在细胞膜和磁小体膜中的产生和掺入。据我们所知，磁性分枝杆菌是第二个通过基因工程具有掺入 PC 的脂质膜的细菌物种。随后，同时表达了 GPCR、促甲状腺激素受体 (TSHR) 和 PCS。我们发现磁小体膜中的 PC 有助于 TSHR 及其配体的结合，表明本研究中证明的遗传方法有助于增强磁小体上展示的 GPCR 的功能。