<p>The F-box domain was first described as a sequence motif found in cyclin-F that interacts with the protein SKP1 [<cite idref="PUB00000938"/>, <cite idref="PUB00000952"/>]. This relatively conserved structural motif is present in numerous proteins and serves as a link between a target protein and a ubiquitin-conjugating enzyme. The SCF complex (e.g., Skp1-Cullin-F-box) plays a similar role as an E3 ligase in the ubiquitin protein degradation pathway [<cite idref="PUB00005810"/>, <cite idref="PUB00005823"/>]. DifferentF-box proteins as a part of SCF complex recruit particular substrates for ubiquitination through specific protein-protein interaction domains.</p><p> Many mammalian F-box domains contain leucine-rich or WD-40 repeats (<db_xref db="INTERPRO" dbkey="IPR001680"/>). However, several F-boxproteins either have other previously described domains such as Sec7 domain found in FBS protein or do not contain defined protein-proteininteraction domains or motifs.</p> F-box domain, cyclin-like