This is a basic part coding for a synthetic chimeric protein. We used Swiss-Model web service to make the 3-D model of ginseng cyclase. Then we used the Chimera software to match the structures of human (1w6k in PDB) and ginseng cyclases.
We found that the first 100 amino acid sequences of two structures were quite different, which indicates obvious species specificity. In order to allow the squalene cyclase to be expressed and function in human cells, we replaced the 100 amino acid residues of N-terminal of the ginseng cyclase with 90 amino acid residues of N-terminal of human cyclase. In addition, we identified five amino acid residues of leader sequence in possible steric conflict to the ginseng cyclase, so we mutated them. The synthetic protein once produced in human cells is designed to make ginsenoside precursors in situ.