ASSIGNMENT OF LOG-NORMAL COMPONENTS OF FLUORESCENCE-SPECTRA OF SERINEPROTEASES TO THE CLUSTERS OF TRYPTOPHAN RESIDUES

The two log-normal spectral components in, alpha-chymotrypsin, trypsin ogen and beta-trypsin fluorescence and the single component of chymotr ypsinogen A emission were analyzed using characteristics of microenvir onment of atoms of indolic fluorophores of individual tryptophan resid ues in the three-dimensional structures of the proteins. Tryptophan re sidues (eight ones in chymotrypsinogen A and alpha-chymotrypsin and fo ur ones in trypsinogen and beta-trypsin) in these homologous proteins form three clusters with resonance excitation energy exchange between fluorophores within each of them. In all the proteins, Trp51 and 141 d etermine the shorter-wavelength spectral components (ca. 330 nm) and T rp215 and 237 emit as longer-wavelength ones (ca. 340 nm). Excited sta tes of fluorophores of Trp27, 29, 207 (cluster A) and 172 (in cluster B) are deactivated by the near disulfide bonds. The longer-wavelength component is quenched in chymotrypsinogen emission due probably to the formation of an electron trap including Asn91 amide and several water molecules. The contribution of longer-wavelength component in trypsin spectrum increases comparing with that of trypsinogen due to some lit tle changes in localization and a huge rise of mobility of Met180 sulf ur atom nearly Trp215 in trypsin.