PROLINE-PROTEIN INTERACTIONS - PROTECTION OF STRUCTURAL AND FUNCTIONAL INTEGRITY OF M(4) LACTATE-DEHYDROGENASE

A well defined labile isozyme, rabbit muscle M4 - lactate dehydrogenas e was denatured under freeze-thaw, heat and GuHCl treatment in the pre sence and absence of proline, and the corresponding structural changes of the enzyme were monitored through fluorescence and CD spectral stu dies. The data reveal that proline confers protection to the structura l integrity of the enzyme, thereby protecting its activity. This was a ttributed to its property of forming hydrophilic colloids in aqueous m edia with a hydrophobic backbone interacting with protein. Unlike othe r osmolytes, proline is proposed to act on the enzyme stability not on ly by inducing preferential hydration of proteins but also through the interactions of its multimeric hydrophobic backbone with the solvent- accessible hydrophobic regions of the enzyme. (C) 1994 Academic Press, Inc.