Structural and biophysical characterization of photoswitchable peptides and their complexes

Networks of biomacromolecular interaction form the core of internal cellular logic where a wide range of input signals get analysed and results in a genetically programmed output. This description holds not only for healthy cells but is true also for those virally infected when a virus implements new biomacromolecular elements and modifies existing networks. Those hostile interactions are crucial for the HIV virus replication cycle. Due to the scale-free nature of biomacromolecular interaction networks they are prone to malfunction if a hub (node with the highest interactions) is damaged. Perhaps the best example of such a situation can be observed in the apoptotic machinery. Overexpression, deletion or mutations (depending on the context) in apoptotic proteins can lead to various diseases, most prominently cancer. Therefore current research efforts concentrate on designing inhibitors of malfunctioning interactions. Occasionally interaction between the two binding partners relies on a well-defined secondary structures element. This allows to engineer this element and use it to bias the given interaction equilibrium towards dissociation. One such approach concentrates on α-helices that are crosslinked with azobenzene derivatives. This permits not only to increase the helical content of a peptide, which translates to increased affinity (potency), but transplants a photo-controllability. Photoswitchable peptides created in this way can be controlled externally; their affinity towards targets can be effectively photomodulated. The first chapter of the thesis concentrates on the development and evaluation of photocontrollable peptides derived from the arginine rich region of the HIV type I Rev protein. Rev, which is an early product generated from the HIV genome, binds to RRE containing mRNA and removes it from the nucleus, allowing expression of unspliced or singly spliced mRNA into different protein products. As a consequence the RRE-Rev interaction controls the infect