Structures of mouse DUOX1–DUOXA1 provide mechanistic insights into enzyme activation and regulation

DUOX1, a NADPH oxidase family member, catalyzes the production of hydrogen peroxide. DUOX1 is expressed in various tissues, including thyroid and respiratory tract, and plays a crucial role in processes such as thyroid hormone biosynthesis and innate host defense. DUOX1 co-assembles with its maturation factor DUOXA1 to form an active enzyme complex. However, the molecular mechanisms for activation and regulation of DUOX1 remain mostly unclear. Here I present cryo-EM structures of the mammalian DUOX1–DUOXA1 complex, in the absence and presence of substrate NADPH, as well as DUOX1–DUOXA1 in an unexpected dimer-of-dimer configuration. These structures reveal atomic details of the DUOX1–DUOXA1 interaction, a lipid-mediated NADPH-binding pocket and the electron transfer path. Furthermore, biochemical and structural analyses indicate that the dimer-of-dimer configuration represents an inactive state of DUOX1–DUOXA1, suggesting an oligomerization-dependent regulatory mechanism. Together, my work provides structural bases for DUOX1–DUOXA1 activation and regulation.