Component of an E3 ubiquitin ligase complex that plays a central role in blue light-dependent circadian cycles. Acts as a blue light photoreceptor, due to the presence of FMN, that mediates light-regulated protein degradation of critical clock components by targeting them to the proteasome complex (By similarity). Protein modification; protein ubiquitination. FMN binds covalently to cysteine after exposure to blue light and is reversed in the dark. Belongs to the ADAGIO family.