Effect Of Chemical Modification On The Molecular Chaperone Function Of Trigger Factor

Proteostasis is maintained by a plethora of factors. An emerging concept of recent research is that these components function as a coordinated Proteostasis Network(PN).Chaperones play important roles in all functions of the PN. Newly synthesized proteins often need the assistance of molecular chaperones to efficiently fold into the three-dimensional structures with unique function. Escherichia coli trigger factor(TF) is the best-characterized ribosome-associated chaperone and the first molecular chaperone interacting with nascent chains.After the analysis of structure of TF, we found that some regions on the surface of TF maybe were involved in chaperone function of TF. In order to clarify the importance of the 14 regions and their influence on the function of TF, we replaced these regions with Cys residue by site-directed mutagenesis, and then chose iodacetamide,indole-3-acetic acid, 2-bromoethylamine hydrobromide and N-phenylmaleimide to modify the sulfhydryl of Cys. We investigated whether the regions are involved in the function of TF by detecting the chaperone activity on the refolding and aggregation of denatured proteins glyceraldehyde-3-phosphate dehydrogenase and lysozyme,. At last, it was found that the roles of the 14 regions in the chaperone function of TF were closely related to their physicochemical properties, such as hydrophobicity, polarity and charge.It was found that the effects of the same chemical modification on chaperone activity of TF were different when different proteins were used as substrate, indicating that the folding assistance provided by TF was substrate identity- dependent.The study will give us a deeper understanding of molecular mechanism of TF as well as a theoretical basis for optimizing the molecular chaperones system and improving the heterologous proteins’ expression efficiency in E. coli.