We earlier documented the structural and functional characterization of PeIF5B factor from Pisum sativum that shows strong homology to the universal translation initiation factor eIF5B (Rasheedi et al., 2007, 2010 [12,13]). We now show that PeIF5B is an unusually thermo-stable protein resisting temperatures up to 95 degrees C. PeIF5B prevents thermal aggregation of heat labile proteins, such as citrate synthase (CS) and NdeI, under heat stress or chemical denaturation conditions and promotes their functional folding. It also prevents the aggregation of DTT induced insulin reduction. GTP appears to stimulate PeIF5B-mediated chaperone activity. In-vivo. PeIF5B over expression significantly enhances, the viability of Escherichia coil cells after heat stress (50 degrees C). These observations lead us to conclude that PeIF5B, in addition to its role in protein translation, has chaperone like activity and could be likely involved in protein folding and protection from stress. (C) 2011 Elsevier Inc. All rights reserved.