The photosystem II complex of oxygenic photosynthesis oxidizes waterto oxygen at a Mn4Ca metallocluster. This is the only known systemthat can catalyse this reaction at room temperature, with visiblelight and with cheap metal catalysts. An efficient and cheapartificial water-oxidising catalyst would have a key role to play inthe development of artificial photosynthetic systems that could beused to generate fuel directly from sunlight and water.  Thecomplexity of such a catalyst could be mimicked by using a simpleprotein to ligate the metallocluster, with ligand positions copiedfrom photosystem II. Different families of natural proteins can use asimilar technique - the trypsin and subtilisin families of serineproteases use near-identical catalytic Ser-His-Asp catalytic triadswith radically different protein folds. Such design, based on 'inverserotamers' has been used to transplant ligand binding sites into hostproteins, and even construct novel enzyme activities by placingresidues corresponding to transition states into host proteins. Aswell as natural proteins, artificial proteins can be used for suchtransplants, including four helical bundle maquettes, and a novelclass of synthetic beta-helical proteins to be discussed. These hostproteins can be used to bind several cofactors and functional sites,linked into a single functional unit.

Protein design for artificial photosynthesis

247th National Meeting (2014)

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