the human "fbxl3" gene is located on the long arm of chromosome 13 at position 22.3. the protein is composed of 428 amino acids and has a mass of 48,707 daltons. the fbxl3 protein contains an f-box domain, characterized by a 40 amino acid motif that mediates protein-protein interactions, and several tandem leucine-rich repeats used for substrate recognition. it has eight post-translational modification sites involving ubiquitination and four sites involving phosphorylation. the fbxl3 protein is predominantly localized to the nucleus. it is one of four subunits of a ubiquitin ligase complex called skp1-cul1-f-box-protein, which includes the proteins cul1, skp1, and rbx1.