The allosteric interaction between D-galactose and the Escherichia coli galactose repressor protein.

摘要: The Escherichia coli galactose repressor protein (GalR) inhibits transcription of the gal operon upon binding to two operator sites (1-7). This DNA activity is inhibited when D-galactose or D-fucose binds GalR (8-14). Fluorescence spectroscopy was used characterize single tryptophan and investigate interaction between GalR. quenching experiments place both residues dimer in similar, solvent-exposed locations. Galactose shown enhance intrinsic fluorescence GalR, source which not explained by a change decay times, but due an increase pre-exponential factor longest three times. It that beta-anomer likely form An pH from 6.3 9.5 causes equilibrium association constant (K alpha) describing galactose-GalR decrease 10-fold. cooperative below 9.5. Over range 9.5, solvent exposure increases. also induces exposure. These results, others presented this paper, show cause global alterations structure