CryoEM structure of the reduced form of human MICAL1, the multidomain flavoenzyme participating in actin cytoskeleton dynamics

Human MICAL1 belongs to the MICAL family of multidomain enzymes that control actin cytoskeleton dynamics and related processes through their F-actin depolymerising activity. The latter is due to the NADPH-dependent H2O2-producing reaction of the N-terminal FAD-containing catalytic domain, consisting of reduction of the flavin (FAD) coenzyme by NADPH followed by reduction of O2 and oxidation of target proteins with regeneration of the oxidised coenzyme. The catalytic domain is followed by regulatory domains that lead to an autoinhibited MICAL1 form in the free “as isolated” state. Thanks to the first data collection session at ESRF CM01 (MX2618) we obtained a reconstruction at 3.2 Å resolution and built a model of full-length MICAL1 in the “closed” autoinhibited oxidised form. To clarify the mechanism of autoregulation of the activity we now wish to tackle the structural characterization of the NADPH-reduced enzyme.