F-box protein

F-box proteins are proteins containing at least one F-box domain. The first identified F-box protein is one of three components of the SCF complex, which mediates ubiquitination of proteins targeted for degradation by the proteasome. F-box proteins have also been associated with cellular functions such as signal transduction and regulation of the cell cycle. In plants, many F-box proteins are represented in gene networks broadly regulated by microRNA-mediated gene silencing via RNA interference. In human cells, in high-iron condition, two iron atoms stabilise the F-Box FBXL5 and then the complex mediates the ubiquitination of IRP2.

The F-box domain is a protein structural motif of about 50 amino acids that mediates protein–protein interactions. It was first identified in cyclin F. 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.