Chemical exchange of hydrogen atoms is the basis for many biological processes, including energy conversion from light into chemical potentials. In a recent collaborative study of the SFB 1078 under the direction of Hartmut Oschkinat (B1), Peter Hegemann (B1, B2) and Roland R. Netz (C1), proton exchange was detected and characterized in the light-driven proton pump bacteriorhodopsin, a well-established model system for protonation dynamics studies. The work, published in the new open access journal Communications Biology of the Nature Publishing Group, revealed that reversible proton translocation occurs even in the dark-state of the protein, involving the retinal Schiff base and D85 exchanging protons with H₂O. The authors find evidence of an active site proton cage and possible proton transfer via R82. The experimental observations have been corroborated by theoretical approaches, further extending the general understanding of proton exchange in proteins.

Friedrich, D., Brünig, F. N., Nieuwkoop, A. J., Netz, R. R., Hegemann, P., and Oschkinat, H. (2020). Collective exchange processes reveal an active site proton cage in bacteriorhodopsin. Communications Biology 3, Article Number 4. doi: 10.1038/s42003-019-0733-7.