Transient increase of tryptophan fluorescence of enzyme caused by photoexcitation of ligand in luciferase-luciferin complex

An experiment was proposed and accomplished that was based on the hypothesi s of the dissociation of the luciferase-luciferin complex in photoexcitatio n. A pump-probe experiment was performed with the use of picosecond laser p ulses and was based on the effect of quenching of enzyme tryptophan fluores cence caused by luciferin binding. A photoinduced increase of the tryptopha n fluorescence intensity was detected. Experimental results were interprete d on the basis of the assumptions on photoinduced dissociation of the lucif erin-luciferase complex and Forster energy transfer from tryptophan to luci ferin. Under the assumption on the photoinduced dissociation and stationary quenching of tryptophan fluorescence the rate of propagation of the confor mational changes in the protein caused by the complex dissociation was esti mated to be >20 m/s. (C) 1999 John Wiley & Sons, Inc.