The dynamics of proton transfer between the bulk and an indicator attached to a defined site on a protein (bacteriorhodopsin) was measured in the time resolved domain. The labelling was attached to the cytoplasmic surface of the protein at the opening of its proton conducting channel (residue 38). Detailed analysis of the results indicates that a nearby carboxylate (aspartate 36) functions as a relay group that accelerates the entrance of proton to the channel. A farther located cluster, of 3 carboxylates, also functions in the same mode. These observations indicate that the surface of the protein had evolved as a functional element in directing the substrate towards the active site.