Small Molecule Modulation of the Archetypal UbiB protein COQ8

Small molecule tools have enabled mechanistic investigations and therapeutic targeting of the protein kinase-like (PKL) superfamily. However, such tools are still lacking for many PKL members, including the highly conserved and disease-related UbiB family. Here, we sought to develop and characterize inhibitor and activator molecules for the archetypal UbiB member, COQ8, whose function is essential for coenzyme Q (CoQ) biosynthesis. Guided by crystallography, activity assays, and cellular CoQ measurements, we repurposed the 4-anilinoquinoline scaffold to selectively inhibit human COQ8A in cells. Second, using 1H-13C HMQC NMR and hydrogen-deuterium exchange mass spectrometry, we reveal that the CoQ precursor mimetic, 2-propylphenol (2-PP), modulates the quintessential UbiB KxGQ domain to increase COQ8A nucleotide affinity and ATPase activity. Our newfound chemical tools promise to lend new mechanistic insights into the activities of these widespread and understudied proteins and to offer potential therapeutic strategies for human diseases connected to their dysfunction.