| F-box linker domain | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 Structure of the LRR linker domain of Skp2 in the Skp1-Skp2 complex.[1] | |||||||||
| Identifiers | |||||||||
| Symbol | F-box | ||||||||
| Pfam | PF00646 | ||||||||
| Pfam clan | CL0271 | ||||||||
| InterPro | IPR001810 | ||||||||
| SMART | SM00256 | ||||||||
| PROSITE | PS50181 | ||||||||
| SCOP2 | 1fs2 / SCOPe / SUPFAM | ||||||||
| Membranome | 630 | ||||||||
| |||||||||
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 26S proteasome.
F-box domain is a protein structural motif of about 50 amino acids that mediates protein–protein interactions. It has consensus sequence and varies in few positions. It was first identified in cyclin F.[2] The F-box motif of Skp2, consisting of three alpha-helices, interacts directly with the SCF protein Skp1.[3] F-box domains commonly exist in proteins in cancer with other protein–protein interaction motifs such as leucine-rich repeats (illustrated in the Figure) and WD repeats, which are thought to mediate interactions with SCF substrates.[4]
F-box proteins have also been associated with cellular functions such as signal transduction and regulation of the cell cycle.[5] In plants, many F-box proteins are represented in gene networks broadly regulated by microRNA-mediated gene silencing via RNA interference.[6] F-box proteins are involved in many plant vegetative and reproduction growth and development. For example, F-box protein-FOA1 involved in abscisic acid (ABA) signaling to affect the seed germination.[7] ACRE189/ACIF1 can regulate cell death and defense when the pathogen is recognized in the Tobacco and Tomato plant.[8]
In human cells, under high-iron conditions, two iron atoms stabilise the F-Box FBXL5 and then the complex mediates the ubiquitination of IRP2.[9]
F-box protein levels can be regulated by different mechanisms. The regulation can occur via protein degradation process and association with SCF complex . For example, in yeast, the F-box protein Met30 can be ubiquitinated in a cullin-dependent manner.[10][11]