A SPARSE-MATRIX SCREEN TO ESTABLISH INITIAL CONDITIONS FOR PROTEIN RENATURATION

Protein renaturation is of particular interest not only for the basic mechanisms of protein folding but also as a practical problem for proteins overexpressed in microorganisms, since recombinant proteins may accumulate as misfolded aggregates in ''inclusion bodies'' that are inactive after purification. We have established a systematic screening method to identify conditions which promote protein renaturation. A matrix of 50 different buffers, which were originally developed for protein crystallization, were found to facilitate the renaturation for eight of nine different proteins examined. The proteins tested include the adhesive protein bindin, recombinant bindin, and a variety of enzymes, including bacterial alkaline phophatase, horseradish peroxidase, lysozyme, trypsin, beta-galactosidase, rabbit carboxylesterase, and acetylcholinesterase. The total amount of activity recovered varied hom 9 to 333% depending on the protein. The conditions that were found to promote renaturation are very different from the optimal conditions for enzyme activity. The finding that most of the proteins tested renatured to a significant extent in one or more of the buffers in the matrix suggests that the sparse matrix screen may be of general utility for establishing initial renaturation conditions for a wide variety of proteins. Once initial renaturation conditions have been identified, the conditions may be optimized by systematically altering other parameters of the renaturation process. (C) 1995 Academic Press, Inc.