Arc Repressor will not Denature Under Pressure in the Absence of Water

• DOI: 10.1006/jmbi.1994.1433
• Publication Date: 2002-10-07T12:32:07Z
• Authors: Andrea C. Oliveira; Luciane P. Gaspar; Andrea T. Da Poian; Jerson L. Silva
• Keywords: DNA-Binding Proteins; Repressor Proteins; 0301 basic medicine; Protein Denaturation; Protein Folding; Viral Proteins; 03 medical and health sciences; Protein Conformation; Thermodynamics; Water; Viral Regulatory and Accessory Proteins

Hydration forces are believed to play a determining role in protein folding. We have examined the contribution of water for the stability of the native dimer state of Arc repressor, a DNA-binding protein. Hydrostatic pressure was utilized to convert Arc repressor protein from a native state to a denatured, molten-globule state at decreasing concentrations of water. The volume change associated with Arc denaturation fell linearly with the increase in concentration of glycerol, whereas the free energy of the reaction increased. The pressure that promotes 50% denaturation (p1/2) increased in direct proportion to the concentration of glycerol or the decrease of water. Extrapolated to zero concentration of water, the data indicate that pressure denaturation would not occur without water. It is concluded that water plays a crucial role in decreasing the stability of a protein to a level that is compatible with its biological properties.