Catcher/Tag cyclization introduces electrostatic interaction mediated protein-protein interactions to enhance the thermostability of luciferase

Efficiently engineering proteins to enhance their thermostability and other features hinges on the correct understanding and prediction of the effects of protein backbone topology and dynamics. Here, we fused a Catcher module to the C-terminus of luciferase and a Tag module to the N-terminus, so that the spontaneous reaction between the Catcher and Tag covalently cyclized the luciferase. The thermal stability of cyclized luciferase improved, with T ₅₀ , t _1/2 , and T _m values higher by 8.9 °C, 2.1-fold and 7.3 °C respectively compared with the linear enzyme. Furthermore, MD simulations suggested that the cyclizations resulted in a tight docking between Catcher/ Tag and luciferase. A series of interactions on the interface between Catcher/Tag and the C-domain of luciferase were identified. Compared with the uncyclized enzyme, these interactions appear to impose remarkable changes to the backbone dynamics of the enzyme. Our data showed that the cyclization increased the gyration radii, and decreased both RMSD values and Cα-fluctuations of the enzyme, which was consistent with experimental observations and indicates that the cyclized luciferase adopted a more stable conformation enssemble. Taken together, this study provides a theoretical understanding of how Catcher/Tag cyclization can enhance the thermal resilience of enzymes, and might be useful in guiding protein design.