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Thermodynamics of binding of D-galactose and deoxy derivatives thereof to the L-arabinose-binding protein

Lookup NU author(s): Professor Steve Homans

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Abstract

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 ΔG°int at 308 K for the 1-, 2-, 3-, and 6-hydroxyl groups of galactose is remarkably constant (−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 (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.

Publication metadata

Author(s): Daranas AH, Shimizu H, Homans SW

Publication type: Article

Publication status: Published

Journal: Journal of the American Chemical Society

Year: 2004

Volume: 126

Issue: 38

Pages: 11870-11876

ISSN (print): 0002-7863

ISSN (electronic): 1943-2984

Publisher: American Chemical Society

URL: http://dx.doi.org/10.1021/ja048054m

DOI: 10.1021/ja048054m

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