FBXL4F-box and leucine-rich repeat protein 4 is a protein that in humans is encoded by the FBXL4 gene.StructureThis gene encodes a member of the F-box protein family which is characterized by an approximately 40 amino acid motif, the F-box. The F-box proteins constitute one of the four subunits of ubiquitin protein ligase complex called SCFs, which function in phosphorylation-dependent ubiquitination. The F-box proteins are divided into 3 classes: Fbws containing WD-40 domains, Fbls containing leucine-rich repeats, and Fbxs containing either different protein-protein interaction modules or no recognizable motifs. The protein encoded by this gene belongs to the Fbls class and, in addition to an F-box, contains at least 9 tandem leucine-rich repeats.Clinical significanceMutations in this gene cause early-onset mitochondrial encephalomyopathy.