Gene H-transfer: bile acid receptor in E.coli & proteorhodpsin in mitochindrial inner membrane


In order to celebrate the power of gene H(orizontal)-transfer between pro- and eukaryotes, we constructed two fusion proteins and tested their function: (1) a synthetic bile acid receptor in E.coli using a mammalian nuclear receptor LXR. As proof-of-principle, the regulatory circuit in symbiotic bacteria could be harmoniously linked to metabolic pathway of their host. Potential application includes in situ synthesis of pharmaceuticals on-demand in the digestive tract. (2) a synthetic light-driven proton pump in human mitocondrial inner membrane using a bacterial proteorhodopsin. Preliminary testing demonstrated cellular sensitivity to light radiation. Application and utility relies on result of in-depth characterization of such system design.

Using lacI DNA-binding domain and LXRbeta ligand-binding domain, we made an artificial bile acid receptor which can regulate expression of target gene within a natural lacI operon. As proof of principle, we demonstrated that regulation of bacteria gene expression by host eukaryocyte metabolites is achievable using chimeric nuclear receptors. Through directed molecular evolution, a harmonious signal network regulating metabolism of both prokaryocytes and their host eukaryocytes in the digestive tract is feasible.


First "reversely" discovered from proteobacteria in 2000,proteorhodopsin (PR) acts as a light-activated proton pump and generates proton motive force across the membrane. We modified PR gene coding sequence by replacing its precusor sequence with the leader peptide of human cytochrome cxidase subunit 4 isoform 1, targeting mitochondrial inner membrane. In addition, all the codons were optimized according to codon usage bias for Homo sapiens. As a result, we made a synthetic light-driven proton pump and positioned it on the inner membrane of mitochondria, which under certain conditions, can positvely use light energy to drive human cells in vitro.