Expression characterization and preparation of human amyloid precursor protein in Escherichia coli

To analyze whether expressed amyloid precursor protein(APP) existed in hydrophilic(cytoplasmid) or hydrophobic( lipid bilayer) environment in E. coli and to obtain intact APP for study on its function, we investigated the expression characterization and preparation of the three intact isoforms APP770, APP751, and APP695 in E. coli. The results show that these expressed APPs existed both in hydrophilic cytoplasm region as inclusion bodies and hydrophobic membrane region as membrane-bound state in E. coli. APPs in inclusion bodies were purified on an NTA-Ni²⁺ agarose column after dissolving in the urea buffer and APPs in membrane-bound state were obtained by ultracentrifugation. The activity analysis indicates that APP770 and APP751 exhibited strong trypsin-inhibitory activity like the natural ones. These results indicate that E. coli cells can be used as host cells for the expression of human integral membrane protein like APP in either soluble or membrane-bound state unless the interest protein undergone post-translational modification is required.