A group at UCSF is re-thinking the role of protonation in regards to protein function. Rapid, reversible, environmentally sensitive and enzyme-free, protonation seems to be an ideal post-translational modification. The authors convincingly make their case with numerous examples of proteins that change activity or conformation with protonation, including actin networks, GEFs, and prion proteins. -SD
Schönichen A, Webb BA, Jacobson MP, Barber DL. 2013.
Considering Protonation as a Post-translational Modification Regulating Protein Structure and Function. Ann. Rev. Biophys. 42: 289–314 doi:10.1146/annurev-biophys-050511-102349