F-box is a protein structural motif of about 50 amino acids that was first found in cyclin F. F-box protein is one of three components of the SCF complex, which mediates ubiquitination of proteins targeted for degradation by the proteasome. The F-box motif interacts directly with the SCF protein Skp1, and F-box domains commonly exist in proteins in concert with other protein-protein interaction motifs such as leucine-rich repeats and WD repeats, which are thought to mediate interactions with SCF substrates. Members of F-box family mediate protein-protein interactions in a variety of contexts, such as polyubiquitination, transcription elongation, centromere binding and translational repression. In plants, many F-box proteins are represented in gene networks broadly regulated by microRNA-mediated gene silencing via RNA interference (1).

1. http://pfam.xfam.org/family/PF00646