Bioengineering of bacterial magnetic particles and its application to estrogen receptor-ligand binding assay

Magnetic particles are used for various biomedical applications because they are easy to both handle and separate from biological samples. Nano-sized bacterial magnetic particles (BacMPs) that display the human estrogen receptor ligand binding domain (ERLBD) on their surfaces were successfully produced by the magnetotactic bacterium, Magnetospirillum inagneticum AMB-1. A receptor assay for endocrine-disrupting chemicals using ERLBD- displaying BacMPs was developed. A BacMP membrane-specific protein, Mmsl6 or Mmsl3, was used as an anchor protein to localize the ERLBD on the surfaces of BacMPs. ERLBD- BacMP complexes were assayed for competitive binding of alkaline phosphatase- conjugated 17(3-estradiol (ALP-E2). Inhibition curve of ALP-E2 to the powerful antagonist, tamoxifen was generated by measuring decreases in luminescence intensity that resulted from the enzymatic reaction of alkaline phosphatase. The overall simplicity of this receptor-binding assay results in a method that can be easily adapted to a high-throughput format.