We have succeeded in developing a simple and effective protein refolding method using the inorganic catalyst, beta-zeolite. The method involves the adsorption of proteins solubilized with 6 M guanidine hydrochroride from inclusion body (IB) preparations onto the zeolite. The denaturant is then removed, and the proteins in the IBs are released from the zeolite with polyoxyethylene detergent and salt. All of the IBs tested (11 different species) were successfully refolded under these conditions. The refolded proteins are biochemically active, and NMR analysis of one of the proteins (replication protein A 8) Supports the conclusion that correct refolding does occur. Based on these results, we discuss the refolding mechanism. (C) 2005 Elsevier Inc. All rights reserved.