Zephyr, J. | Search bioRxiv

bioRxiv2023

FruitFire: a luciferase based on a fruit fly metabolic enzyme

Firefly luciferase is homologous to fatty acyl-CoA synthetases from insects that are not bioluminescent. Here, we determined the crystal structure of the fruit fly fatty acyl-CoA synthetase CG6178 to 2.5 [A]. Based on this structure, we mutated a steric protrusion in the active site to create the artificial luciferase FruitFire, which prefers the synthetic luciferin CycLuc2 to D-luciferin by >1000-fold. FruitFire enabled in vivo bioluminescence imaging in the brains of mice using the pro-luciferin CycLuc2-amide. The conversion of a fruit fly enzyme into a luciferase capable of in vivo imaging underscores the potential for bioluminescence with a range of adenylating enzymes from nonluminescent organisms, and the possibilities for application-focused design of enzyme-substrate pairs.

biochemistry↗

bioRxiv2021

Deciphering the Molecular Mechanism of HCV Protease Inhibitor Fluorination as a General Approach to Avoid Drug Resistance

Third generation Hepatitis C virus (HCV) NS3/4A protease inhibitors (PIs), glecaprevir and voxilaprevir, are highly effective across genotypes and against many resistant variants. Unlike earlier PIs, these compounds have fluorine substitutions on the P2-P4 macrocycle and P1 moieties. Fluorination has long been used in medicinal chemistry as a strategy to improve physicochemical properties and potency. However, the molecular basis by which fluorination improves potency and resistance profile of HCV NS3/4A PIs is not well understood. To systematically analyze the contribution of fluorine substitutions to inhibitor potency and resistance profile, we used a multi-disciplinary approach involving inhibitor design and synthesis, enzyme inhibition assays, co-crystallography, and structural analysis. A panel of inhibitors in matched pairs were designed with and without P4 cap fluorination, tested against WT protease and the D168A resistant variant, and a total of 22 high-resolution co-crystal structures were determined. While fluorination did not significantly improve potency against the WT protease, PIs with fluorinated P4 caps retained much better potency against the D168A protease variant. Detailed analysis of the co-crystal structures revealed that PIs with fluorinated P4 caps can sample alternate binding conformations that enable adapting to structural changes induced by the D168A substitution. Our results elucidate molecular mechanisms of fluorine-specific inhibitor interactions that can be leveraged in avoiding drug resistance.

biochemistry↗