STEADY-STATE AND TIME-RESOLVED FLUORESCENCE STUDIES ON THE LIGAND-INDUCED CONFORMATIONAL CHANGE IN AN ACTIVE LYSOZYME DERIVATIVE, KYN62-LYSOZYME

The ligand-induced conformational change of an active lysozyme derivat ive, Kyn62-lysozyme, in which Trp62 of hen egg-white lysozyme (EC 3.2. 1.17) was selectively modified to kynurenine, was investigated by stea dy-state and time-resolved fluorescence spectroscopy. Kyn62 formed an intramolecular energy transfer donor-acceptor pair with a tryptophan r esidue as a donor. The energy transfer was related to the conformation of the active site. The spectral overlap integral (J) of the kynureni ne-tryptophan pair is large as it was determined to be 4.92 x 10(-15) M(-1) cm(3). Time-resolved fluorescence properties of Kyn62-lysozyme a nd its complex with a trimer of N-acetyl-D-glucosamine [(GlcNAc)(3)] s how that the energy donor is Trp28 or Trp111 in the hydrophobic matrix box of the free Kyn62-lysozyme. In the complex, it appears that the k ynurenine residue drastically changed its orientation or approached cl oser to Trp108 to accept more efficiently the excitation energy from T rp108 on the binding of Kyn62-lysozyme with (GlcNAc)(3).