De Novo Design and Synthesis of Polypeptides Based on Photosystem II

Abstract

Protein design has become a powerful tool to answer fundamental questions concerning protein structure/function relationships. Recently de novo protein synthesis has provided simple, well-defined polypeptide scaffolds that fold into stable structures and allow for the incorporation of biologically relevant cofactors. Here, we report our approach to de novo protein synthesis. We have synthesized a polypeptide that folds into a helix-turn-helix hairpin structure using an E. coli expression system. In order to mimic the donor side of photosystem II, we have engineered two ligation sites into the polypeptide, one to bind a chlorophyll molecule and another to bind a tyrosine analogue. By genetically altering the environment around the chlorophyll-binding site, we hope to adjust the redox poise and thereby to mimic the photo-induced electron transfer of photosystem II.