The photosynthetic reaction centre (RC) is central to the conversion of solar energy into chemical energy and is a model for bio-mimetic engineering approaches to this end. In this seminar, building on earlier studies, bio-engineering of a Photosystem II (PSII) RC inspired peptide model, will be presented. A non-photosynthetic haem containing bacterioferritin (BFR) from E.coli that expresses as a homodimer was used as a protein scaffold, incorporating redox-active cofactors mimicking those of PSII. Desirable properties include: a di-nuclear metal binding site which provides ligands for class II metals, a hydrophobic pocket at the dimer interface which can bind a photosensitive porphyrin and presence of tyrosine residues proximal to the bound cofactors, which can be utilised as efficient electron-tunnelling intermediates.
Light-induced electron transfer from proximal tyrosine residues to the photo-oxidised ZnCe6•+, in the modified BFR reconsitituted with both ZnCe6 and MnII, is presented. Three site-specific tyrosine variants (Y25F, Y58F and Y45F) were made to localise the redox-active tyrosine in the engineered system. The results indicate that: presence of bound MnII is necessary to observe tyrosine oxidation in all BFR variants; Y45 the most important tyrosine as an immediate electron donor to the oxidised ZnCe6•+; and that Y25 and Y58 are both redox-active in this system, but appear to function interchangebaly. High-resolution (2.1 Å) crystal structures of the tyrosine variants show that there are no mutation-induced effects on the overall 3-D structure of the protein. Small effects are observed in the Y45F variant. Here, the BFR-RC represents a protein model for artificial photosynthesis.
Biography: Dr Kastoori Hingorani is a visiting research fellow at the Research School of Biology (RSB), The Australian National University (ANU). The seminar will present the research that was conducted by her during her PhD with Associate Professor Warwick Hillier and ProfessorTom Wydrzynski. Inspired by the advances in artificial photosynthesis and protein engineering, her research at ANU focussed on designing and engineering protein models for novel applications in providing clean energy alternatives. For her post-doctoral research at ANU, she worked with the cyanobacterium species T. elongatus for applications in bioenergy, biotechnology and photosystem II studies. She continues to be inspired by photosynthetic microorganisms – algae and cyanobacteria and says “these are very advanced, nature's own solar panels and carbon sequestering systems and there are important lessons to be learnt”. Kastoori now works in the research commercialisation and technology transfer space – taking promising science to the field.