title: Protein free energy landscapes remodeled by ligand binding.
abstract: Glucose/galactose binding protein (GGBP) functions in two different larger systems of proteins used by enteric bacteria for molecular recognition and signaling. Here we report on the thermodynamics of conformational equilibrium distributions of GGBP. Three fluorescence components appear at zero glucose concentration and systematically transition to three components at high glucose concentration. Fluorescence anisotropy correlations, fluorescent lifetimes, thermodynamics, computational structure minimization, and literature work were used to assign the three components as open, closed, and twisted conformations of the protein. The existence of three states at all glucose concentrations indicates that the protein continuously fluctuates about its conformational state space via thermally driven state transitions; glucose biases the populations by reorganizing the free energy profile. These results and their implications are discussed in terms of the two types of specific and nonspecific interactions GGBP has with cytoplasmic membrane proteins.
authors.affiliation: Department of Chemistry and Chemical Biology, The State University of New Jersey, Piscataway, New Jersey 08854, USA.
authors.forename: Troy C
authors.initials: TC
authors.lastname: Messina
authors.forename: David S
authors.initials: DS
authors.lastname: Talaga
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D055592:Biophysical Phenomena; D001703:Biophysics; D004755:Enterobacteriaceae / Q000378:metabolism*; D005454:Fluorescence Polarization; D005690:Galactose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D008024:Ligands; D008565:Membrane Proteins / Q000378:metabolism; D008958:Models, Molecular; D009004:Monosaccharide Transport Proteins / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D008024:Ligands; D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; D005947:Glucose; D005690:Galactose