RESUMO
Proton-transfer proteins are often exposed to the bulk clusters of carboxylate groups that might bind protons transiently. This raises important questions as to how the carboxylate groups of a protonated cluster interact with each other and with water, and how charged protein groups and hydrogen-bonded waters could have an impact on proton transfers at the cluster. We address these questions by combining classical mechanical and quantum mechanical computations with the analysis of cyanobacterial photosystem II crystal structures from Thermosynechococcus elongatus. The model system we use consists of an interface between PsbO and PsbU, which are two extrinsic proteins of photosystem II. We find that a protonated carboxylate pair of PsbO is part of a dynamic network of protein-water hydrogen bonds which extends across the protein interface. Hydrogen-bonded waters and a conserved lysine sidechain largely shape the energetics of proton transfer at the carboxylate cluster.
RESUMO
This perspective article highlights the challenges in the theoretical description of photoreceptor proteins using multiscale modeling, as discussed at the CECAM workshop in Tel Aviv, Israel. The participants have identified grand challenges and discussed the development of new tools to address them. Recent progress in understanding representative proteins such as green fluorescent protein, photoactive yellow protein, phytochrome, and rhodopsin is presented, along with methodological developments.