Laboratoire d'Optique et Biosciences

We have been investigating and regulating protein and peptide structures. For example, the side chain of the cysteine residue of apoplastocyanin (apoPC) was site-specifically modified with a 4,5-dimethoxy-2-nitrobenzyl derivative, where the modified apoPC was unfolded. The substituent was cleaved by photoirradiation and the native β-sheet structure was recovered after the photocleavage reaction. Copper(II) ion-bound CysGly dipeptides were linked by an azobenzene derivative and the azobenzene linked molecule was photoisomerized between the trans and cis forms. The two copper(II) ion centers were positioned close to each other in the cis form, whereas they were far away from each other in the trans form. The copper complex in the cis form exhibited DNA cleavage activity, whereas the activity in the trans form was negligible. Concerning protein aggregation, it has been known for nearly half a century that cytochrome c (cyt c) forms polymers, but the polymerization mechanism remains unknown. We found that cyt c forms polymers by successive domain swapping, where the C-terminal helix is displaced from its original position in the monomer and Met-heme coordination is perturbed significantly.