Successful Mesoporous Silica Encapsulation of Optimally Functional EcDOS (E. coli Direct Oxygen Sensor), a Heme-based O₂-Sensing Phosphodiesterase

摘要

The heme-based O_(2) sensor from Escherichia coli , Ec DOS, exerts phosphodiesterase activity towards cyclic-di-GMP (c-di-GMP), an important second messenger that regulates biofilm formation, virulence, and other important functions necessary for bacterial survival. Ec DOS is a two-domain protein composed of an N-terminal heme-bound O_(2)-sensing domain and a C-terminal functional domain. O_(2) binding to the heme Fe(II) complex in the O_(2)-sensing domain substantially enhances the catalytic activity of the functional domain, a property with potentially promising medical applications. Mesoporous silica is a useful material with finite-state machine-like features suitable for mediating numerous enzymatic functions. Here, we successfully encapsulated Ec DOS into mesoporous silica, and demonstrated that encapsulated Ec DOS was substantially activated by CO, an alternative signaling molecule used in place of O_(2), exhibiting the same activity as the native enzyme in aqueous solution. Encapsulated Ec DOS was sufficiently stable to exert its enzymatic function over several experimental cycles under aerobic conditions at room temperature. Thus, the present study demonstrates the successful encapsulation of the heme-based O_(2) sensor Ec DOS into mesoporous silica and shows that the native gas-stimulated function of Ec DOS is well conserved. As such, this represents the first application of mesoporous silica to an oxygen-sensing—or any gas-sensing—enzyme.