Time-resolved intrinsic fluorescence of Enzyme I. The monomer/dimer transition.
Enzyme I of the bacterial phosphotransferase system can exist in a monomer/dimer equilibrium which may have functional significance. Each monomer contains two tryptophan residues. It is demonstrated that the decay of both the monomer and the dimer can be described by a biexponential. The decay times depend on the temperature and at 6 degrees C the decay times are tau 1 = 0.4 ns and tau 2 = 3.2 ns for the monomer and tau 3 = 3.2 ns and tau 4 = 7.2 ns for the dimer form of the enzyme. The changes in the fluorescence decay parameters can be utilized to measure the equilibrium constant for the monomer/dimer transition.
Chauvin
F
F
Department of Biology, Johns Hopkins University, Baltimore, MD 21218.
Toptygin
D
D
Roseman
S
S
Brand
L
L
D004926:Escherichia coli / Q000201:enzymology; D007700:Kinetics; D046911:Macromolecular Substances; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism*; D013050:Spectrometry, Fluorescence / Q000379:methods; D013816:Thermodynamics; D013997:Time Factors; D014364:Tryptophan / Q000032:analysis
D046911:Macromolecular Substances; D014364:Tryptophan; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System