Thermodynamics of binding of D-galactose and deoxy derivatives thereof to the L-arabinose-binding protein.
We report the thermodynamics of binding of d-galactose and deoxy derivatives thereof to the arabinose binding protein (ABP). The "intrinsic" (solute-solute) free energy of binding DeltaG degrees (int) at 308 K for the 1-, 2-, 3-, and 6-hydroxyl groups of galactose is remarkably constant (approximately -30 kJ/mol), despite the fact that each hydroxyl group subtends different numbers of hydrogen bonds in the complex. The substantially unfavorable enthalpy of binding (approximately 30 kJ/mol) of 1-deoxygalactose, 2-deoxygalactose, and 3-deoxygalactose in comparison with galactose, cannot be readily accounted for by differences in solvation, suggesting that solute-solute hydrogen bonds are enthalpically significantly more favorable than solute-solvent hydrogen bonds. In contrast, the substantially higher affinity for 2-deoxygalactose in comparison with either 1-deoxygalactose or 3-deoxygalactose derives from differences in the solvation free energies of the free ligands.
Daranas
Antonio Hernandez
AH
Astbury Centre for Structural Molecular Biology, School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, UK.
Shimizu
Hiroki
H
Homans
Steve W
SW
D002151:Calorimetry / Q000379:methods; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D029968:Escherichia coli Proteins; D005643:Fucose / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D005690:Galactose / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D011485:Protein Binding; D013816:Thermodynamics
C016242:AraF protein, E coli; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D005643:Fucose; D005690:Galactose