Critical effect of proline on thermostability of endoglucanase II from Penicillium verruculosum

Thermostability is an important protein property essential for the protein industrial application. Different approaches of rational design are used for protein thermostability improvement. In this research, the effect of proline substitutions on the protein thermostability was tested. Several types of available data on protein characteristics were used for substitution position choosing in order to find those that are critical for thermostability improvement while maintaining the specific activity. The approach used was based on combined analysis of protein structure, structure-function relationship, multiple sequence alignment, and folding free energy. Proline substitutions that were carried out had a critical effect on thermostability of endoglucanase II from Penicillium verruculosum. The most stabilizing substitution S308P provided a 4- and 2.4-fold increase in time of half-life at 70 degrees C and 80 degrees C with maintaining the specific activity. Molecular dynamics simulations revealed the observed effects on the protein structure and indicated principal changes in flexibility and hydrogen bonds networks.