title: Proton shuttle in green fluorescent protein studied by dynamic simulations.
abstract: As a direct simulation of a multistep proton transfer reaction involving protein residues, the proton relay shuttle between A and I forms of green fluorescent protein (GFP) is simulated in atomic detail by using a special molecular dynamics simulation technique. Electronic excitation of neutral chromophore in wild-type GFP is generally followed by excited-state proton transfer to a nearby glutamic acid residue via a water molecule and a serine residue. Here we show that the second and third transfer steps occur ultrafast on time scales of several tens of femtoseconds. Proton back-shuttle in the ground state is slower and occurs in a different sequence of events. The simulations provide atomic models of various intermediates and yield realistic rate constants for proton transfer events. In particular, we argue that the I form observed spectroscopically under equilibrium conditions may differ from the I form observed as a fast intermediate by an anti to syn rotation of the carboxyl proton of neutral Glu-222.
authors.affiliation: Max Planck Institute of Biophysics, Kennedyallee 70, 60596 Frankfurt, Germany.
authors.forename: Markus A
authors.initials: MA
authors.lastname: Lill
authors.forename: Volkhard
authors.initials: V
authors.lastname: Helms
mesh_terms: D003198:Computer Simulation; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000737:chemistry*; D008958:Models, Molecular; D020836:Protein Structure, Quaternary; D011522:Protons
chemical_list: D008164:Luminescent Proteins; D011522:Protons; D049452:Green Fluorescent Proteins