Glucose-Induced Thermal Stabilization of the Native Conformation of GLUT 1

Abstract

The glucose transporter, GLUT 1, was purified from erythrocyte membranes and incorporated into vesicles of erythrocyte lipids. These protein-containing vesicles were studied with differential scanning calorimetry. It was found that the protein underwent an irreversible denaturation at 68.5 +/- 0.2 degreesC (at a scan rate of 0.25 degreesC/min) which was shifted to 72.6 +/- 0.2 degreesC in the presence of 500 mM D-glucose, while 500 mM L-glucose or 10 microM cytochalasin B did not produce a significant shift. The calorimetric enthalpy was found to be 150 kcal/mol, independent of the presence of D-glucose. On a weight basis this value is lower than that for soluble proteins, but it is comparable to values obtained with other integral membrane proteins. The van't Hoff enthalpy is similar to the calorimetric enthalpy, within the experimental error, indicating that the transition is not likely to be cooperative. The activation energy is estimated from both the scan rate dependence of the transition temperature and from the shape of the DSC curve. The presence of 500 mM D-glucose slightly decreases the activation energy. It is concluded that the shift to a higher denaturation transition temperature in the presence of D-glucose is not a result of increased kinetic stability of GLUT 1.

Purification and Characterization of Human Erythrocyte Glucose Transporter in Decylmaltoside Detergent Solution

“…The effects of chemical and physical factors can be tested by incubating the dues in the active site and the ligand. D-Glucose, which increases the thermostability of Glut1 by shifting its protein sample in the presence of the factor at 37ЊC for a few hours, followed by assessment of the stability of denaturation transition to higher temperature (26), also helps to maintain its monodispersity. the protein by analytical size-exclusion chromatography on HLPC.…”

Influence of D‐ and L‐glucose on erythrocytes and blood viscosity

“…no change in centrifuged haematocrit. In contrast, L‐glucose, which is not transported by GLUT‐1 into the RBC [33], remained outside the cell and became osmotically active, leading to cell shrinkage (decreased haematocrit; Fig. 3).…”

Into the Lipid Realm: Stability and Thermodynamics of Membrane Proteins

“…In both cases, however, the presence of the corresponding ligands (glucose and 11-cis retinal, respectively) increase the T m of the thermal transitions, suggesting that the ligand-binding sites can unfold above the thermal transition [90,91].…”

“…Irreversibility and the presence of residual secondary structure in the final thermal state have also been observed in the thermal unfolding of GLUT1 and rhodopsin [90,91], although it is not possible to address the extent of residual structure in the final state from the reported data. In both cases, however, the presence of the corresponding ligands (glucose and 11-cis retinal, respectively) increase the T m of the thermal transitions, suggesting that the ligand-binding sites can unfold above the thermal transition [90,91].…”