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Background: Rifampin is a representative inducer of P-gp, and the only known mechanism is binding between rifampin and PXR. Results: Rifampin directly activates CK2, which phosphorylates Hsp90␤. Consequently, PXR increases, and P-gp expression is induced. Conclusion: A mechanism for inducing P-gp expression by rifampin exposure is newly identified. Significance: A strategy for overcoming P-gp-derived drug resistance is suggested.

Exploiting carbonic anhydrase (CA), an enzyme that rapidly catalyzes carbon dioxide hydration, is an attractive biomimetic route for carbon sequestration due to its environmental compatibility and potential economic viability. However, the industrial applications of CA are strongly hampered by the unstable nature of enzymes. In this work, we introduced in silico designed, de novo disulfide bond in a bacterial α-type CA to enhance thermostability. Three variants were selected and expressed in Escherichia coli with an additional disulfide bridge. One of the variants showed great enhancement in terms of both kinetic and thermodynamic stabilities. This improvement could be attributed to the loss of conformational entropy of the unfolded state, showing increased rigidity. The variant showed an upward-shifted optimal temperature and appeared to be thermoactivated, which compensated for the lowered activity at 25 °C. Collectively, the variant constructed by the rapid and effective de novo disulfide engineering can be used as an efficient biocatalyst for carbon sequestration under high temperature conditions.

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