[Intrinsic fluorescence of globular actin. Features of localization of tryptophan residues].

The contribution of individual Trp residues to alpha-actin fluorescence was evaluated by means of an analysis of their microenvironment, which was done on the basis of PIR-International protein sequence database information. The contribution of Trp79 and Trp86 was shown to be low due to an effective nonradiating energy transfer according to the inductive resonance mechanism between the Trp residues and the fluorescence quenching of Trp86 by S gamma of Cys10, an efficient fluorescence quencher. The intrinsic fluorescence of actin was found to be determined mainly by Trp340 and Trp356, which are internal, inaccessible to solvent, and have a high density microenvironment formed mainly by nonpolar groups of protein. It is possible that the side chain conformation of Trp340 (t-isomer; chi 1 190 degrees, chi 2 89 degrees), aromatic rings of Tyr and Phe residues, and Pro residues in the microenvironment of Trp340 and Trp356 substantially contribute to the short-wavelength fluorescence spectrum of actin.