Small Differences in Tryptophan Fluorescence Spectra of ‘Sodium’ and ‘Potassium’ Forms of (Na⁺, K⁺)‐Dependent Adenosinetriphosphatase

Abstract

A detailed comparative analysis of tryptophan fluorescence spectra of 'sodium' and 'potassium' forms of (Na+, K+)-activated ATPase was carried out. The 'potassium' form spectrum is shifted relatice to that of the 'sodium' form by approximately 0.5 -1 nm towards shorter wavelengths. The maximal amplitude of the difference spectrum for these forms makes up about 2 % of maximal fluorescence intensity of any of the forms. The shape of the difference spectrum does not depend on the solution temperature or ionic strength. The spectral differences between the forms are reversible upon addition of a functionally opposite cation (K' for 'sodium' form and vice versa) into the medium, The results suggest that if the differences in fluorescence spectra of the 'sodium' and 'potassium' forms of (Na', K+)-ATPase resulted from the differences in the protein structure, they may be caused by an alteration in local environment of no more than one or two tryptophan residues.

Design, synthesis, and characterization of a novel hemoprotein

“…To probe the local protein environment in the vicinity of the Trp residues for apo‐ and holo‐6H7H, fluorescence spectroscopy was employed. Tryptophan fluorescence has been used extensively as a probe of local protein environment in natural proteins (Chetverin et al 1980; Lee et al 1989; Viguera et al 1992; Genov et al 1993; Gilardi et al 1994; Chen and Sanyal 1999). In particular, the tryptophan fluorescence maximum, λ F , and full width at half maximum (FWHM) are used as a probe for the extent of solvent exposure: λ F for a buried Trp is 330–332 nm, for a Trp with limited exposure λ F is 340–342 nm, and λ F is 350–353 nm for a Trp exposed to water (Burstein et al 1973).…”