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8191657 
Meetings & Symposia 
Dynamics of protein association: Nanosecond time resolved studies of enzyme I of the PTS 
Chauvin, F; Roseman, S; Brand, L 
1990 
Publ by IEEE 
Piscataway, NJ, United States 
pt 4 
1610-1611 
English 
Nanosecond time-resolved fluorescence methods including time-correlated single-photon counting and phase/modulation techniques are used to investigate the equilibria and kinetics of subunit association/disassociation of Enzyme I of the bacterial sugar phosphotransferase system (PTS). Enzyme I appears to have a key role in the control of bacterial metabolism which may be associated with its monomer/dimer equilibrium. The monomer is enzymatically inactive. The enzyme has been labeled with a single pyrene probe molecule on the C-terminal cysteine residue. Time-resolved fluorescence anisotropy measurements indicate that the rate of dimerization is slow and associated with the appearance of enzymatic activity. The kinetics and equilibria of subunit interaction are modulated by the phosphorylation state of the enzyme and by the presence of substrates.