title: Sugar transport by the bacterial phosphotransferase system. The intrinsic fluorescence of enzyme I.
abstract: Enzyme I of the bacterial phosphoenolpyruvate: glycose phosphotransferase system has 2 tryptophan residues/monomer, as determined spectrophotometrically. The tryptophan fluorescence has been investigated with the aid of nanosecond time-resolved techniques. The decay of the fluorescence intensity was analyzed in terms of a biexponential function. The contribution of the emission associated with the shorter decay constant increases from 17-19% at 1 degree C to 43-44% at room temperature. Decay-associated spectra obtained with Enzyme I indicate different spectral distributions associated with the two decay constants. The measurement of tumbling of Enzyme I as a function of temperature revealed a transition of rotational rates between 5 and 15.5 degrees C. Global analysis allowed decomposition of the anisotropy decay into a formulation consistent with monomer and dimer rotational contributions.
authors.affiliation: Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218.
authors.forename: P
authors.initials: P
authors.lastname: Neyroz
authors.forename: L
authors.initials: L
authors.lastname: Brand
authors.forename: S
authors.initials: S
authors.lastname: Roseman
mesh_terms: D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D008433:Mathematics; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism*; D011487:Protein Conformation; D012486:Salmonella typhimurium / Q000201:enzymology*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics; D014364:Tryptophan
chemical_list: D014364:Tryptophan; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System