PROLINE IS A PROTEIN SOLUBILIZING SOLUTE

The effect of proline on the prevention of trichloroacetic acid (TCA)- induced protein precipitation is studied. It is found that proline at high concentrations (>4.0 M) completely prevents TCA-induced precipita tion of hen egg white lysozyme. Other osmolytes such as ethylene glyco l, glycerol and sucrose fail to prevent the TCA-induced precipitation of lysozyme. Viscosity and 1-anilino-8-naphthalene sulphonic acid bind ing experiments suggest that proline at high concentration forms an or dered supramolecular assembly. Proline is shown to increase the solubi lity of protein due to formation of such higher order assemblies. A mo del of the supra-molecular assembly of proline is proposed and a possi ble in vivo role of the increased levels of proline under water stress is discussed.