THE DYNAMIC FEATURE OF THE PROTON COLLECTING ANTENNA OF A PROTEIN SURFACE

The surface of a protein is a condense matrix of proton binding sites having wide range of pK values. In domains where proton uptake is a pa rt of the catalytic cycle, the surface sites endow the region with spe cial kinetic features which represents the ensemble properties of the proton binding sites. Low pK carboxylate can merge their Coulomb cages to form an extended proton trap, where the binding of a proton to one is rapidly followed by shuttling to another. Neutral pK moieties can act as a temporary proton reservoir which delay the proton at the site , enhancing the probability that upon dissociation it will be taken up by the other elements of the active site. These features had been exp erimentally identified in small model molecules, where detailed kineti c analysis was carried out. On the base of these measurements the dyna mics of protonation of the proton entry sites of bacteriorhodopsin and cytochrome oxidase were investigated. (C) 1998 Elsevier Science B.V.