The peptidyl-prolyl cis-trans isomerase activity of the wheat cyclophilin, TaCypA-1, is essential for inducing thermotolerance in Escherichia coli

• Heterologous expression of a wheat cyclophilin, TaCypA-1, confers thermotolerance to E. coli.
• PPIase activity is essential for heat stress tolerance of E. coli cells.
• TaCypA-1 binds calmodulin in vitro in a Ca2+ -dependent manner.
• CaM-binding domain is localized to 51–71 amino acid residues in the N-terminus of TaCypA-1.

Growth at high temperatures is one of the desired features for industrial applications of microbes, as it results in decrease in contamination and enhanced solubility of certain substrates. In this study, it is demonstrated that heterologous expression of a wheat cyclophilin, TaCypA-1, confers thermotolerance to Escherichia coli. The TaCypA-1 possesses peptidyl-prolyl cis-trans isomerase (PPIase) activity that catalyses cis to trans isomerization of the peptidyl prolyl bonds, a rate limiting step in protein folding. Expression of deleted mutants of TaCypA-1, that lacked PPIase activity, resulted in abrogation of thermotolerance, providing the first evidence that this activity plays a key role in stress tolerance of cells and can be exploited for industrial applications. Further, we also demonstrate that TaCypA-1 interacts with calmodulin (CaM), and the CaM-binding domain is localized to amino acid residues 51–71 in the N-terminus region.