The thermodynamics of the binding of L-arabinose and of D-galactose to the L-arabinose-binding protein of Escherichia coli have been studied by isothermal and scanning calorimetry. The binding reaction with arabinose is characterized by an enthalpy change of -15.3 +/- 0.5 kcal mol-1 at 25 degrees C, and a large decrease in apparent heat capacity, amounting to -0.44 +/- 0.05 kcal K-1 mol-1, which is constant over the temperature range 8 to 30 degrees C. Very similar results were obtained with D-galactose. These calorimetric results have been combined with binding constants determined by equilibrium dialysis (Clark, A. F., Gerken, T. A., and Hogg, R. W. (1982) Biochemistry 21, 2227-2233) to obtain free energy and entropy changes over the range 5 to 30 degrees C, and by extrapolation to 60 degrees C. The protein undergoes reversible unfolding on being heated with an increase in enthalpy at 53.5 degrees C of 151.8 +/- 1.1 kcal mol-1 (169.2 +/- 1.2 kcal mol-1 at 59.0 degrees C) and in apparent heat capacity of 3.16 +/- 0.07 kcal K-1 mol-1. In the presence of arabinose, the unfolding enthalpy is increased to 200.7 +/- 1.8 kcal mol-1 at 59.0 degrees C, the increase being due to the enthalpy of dissociation of the ligand which amounts to 31 kcal mol-1 at the unfolding temperature. The unfolding temperature is increased by the presence of excess arabinose or galactose, an effect which is due solely to displacement by the added ligand of the unfolding-dissociation equilibrium. The thermodynamic data are discussed in connection with the detailed structural information available for this system from x-ray crystallography (Newcomer, M. E., Gilliland, G. L. and Quiocho, F. A. (1981) J. Biol. Chem. 256, 13213-13217, and references cited therein). Study holds ProTherm entries: 2994 Extra Details: additive : EDTA(1 mM), thermodynamics; enthalpy change; heat capacity; free energy;,entropy change; L-arabinose-binding protein
ID: Hm2hVTbQ3
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:20 p.m.
Version: 1
Colors: | D | E | R | H | K | S | T | N | Q | A | V | I | L | M | F | Y | W | C | G | P |
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Structure ID | Release Date | Resolution | Structure Title |
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1ABE | 1992-04-23T00:00:00+0000 | 1.7 | NOVEL STEREOSPECIFICITY OF THE L-ARABINOSE-BINDING PROTEIN |
1ABF | 1992-04-23T00:00:00+0000 | 1.9 | SUBSTRATE SPECIFICITY AND AFFINITY OF A PROTEIN MODULATED BY BOUND WATER MOLECULES |
1APB | 1991-11-15T00:00:00+0000 | 1.76 | A PRO TO GLY MUTATION IN THE HINGE OF THE ARABINOSE-BINDING PROTEIN ENHANCES BINDING AND ALTERS SPECIFICITY: SUGAR-BINDING AND CRYSTALLOGRAPHIC STUDIES |
1BAP | 1991-11-15T00:00:00+0000 | 1.75 | A PRO TO GLY MUTATION IN THE HINGE OF THE ARABINOSE-BINDING PROTEIN ENHANCES BINDING AND ALTERS SPECIFICITY: SUGAR-BINDING AND CRYSTALLOGRAPHIC STUDIES |
2WRZ | 2009-09-03T00:00:00+0000 | 2.2 | Crystal structure of an arabinose binding protein with designed serotonin binding site in open, ligand-free state |
5ABP | 1990-12-26T00:00:00+0000 | 1.8 | SUBSTRATE SPECIFICITY AND AFFINITY OF A PROTEIN MODULATED BY BOUND WATER MOLECULES |
6ABP | 1991-04-25T00:00:00+0000 | 1.67 | SUGAR-BINDING AND CRYSTALLOGRAPHIC STUDIES OF AN ARABINOSE-BINDING PROTEIN MUTANT (MET108LEU) WHICH EXHIBITS ENHANCED AFFINITY AND ALTERED SPECIFICITY |
7ABP | 1991-04-25T00:00:00+0000 | 1.67 | SUGAR-BINDING AND CRYSTALLOGRAPHIC STUDIES OF AN ARABINOSE-BINDING PROTEIN MUTANT (MET108LEU) WHICH EXHIBITS ENHANCED AFFINITY AND ALTERED SPECIFICITY |
8ABP | 1991-04-25T00:00:00+0000 | 1.49 | SUGAR-BINDING AND CRYSTALLOGRAPHIC STUDIES OF AN ARABINOSE-BINDING PROTEIN MUTANT (MET108LEU) WHICH EXHIBITS ENHANCED AFFINITY AND ALTERED SPECIFICITY |
9ABP | 1991-11-15T00:00:00+0000 | 1.97 | A PRO TO GLY MUTATION IN THE HINGE OF THE ARABINOSE-BINDING PROTEIN ENHANCES BINDING AND ALTERS SPECIFICITY: SUGAR-BINDING AND CRYSTALLOGRAPHIC STUDIES |
Percent Identity | Matching Chains | Protein | Accession | Entry Name |
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100.0 | L-arabinose-binding periplasmic protein | P02924 | ARAF_ECOLI |