Discovery of Novel Cyclic Salt Bridge in Thermophilic Bacterial Protease and Study of its Sequence and Structure.

The plausible explanation behind the stability of thermophilic protein is still yet to be defined more clearly. Here, an in silico study has been undertaken by investigating the sequence and structure of protease from thermophilic (tPro) bacteria and mesophilic (mPro) bacteria. Results showed that charged and uncharged polar residues have higher abundance in tPro. In extreme environment, the tPro is stabilized by high number of isolated and network salt bridges. A novel cyclic salt bridge is also found in a structure of tPro. High number of metal ion-binding site also helps in protein stabilization of thermophilic protease. Aromatic-aromatic interactions also play a crucial role in tPro stabilization. Formation of long network aromatic-aromatic interactions also first time reported here. Finally, the present study provides a major insight with a newly identified cyclic salt bridge in the stability of the enzyme, which may be helpful for protein engineering. It is also used in industrial applications for human welfare.