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24  structures 86  species 0  interactions 990  sequences 30  architectures

Family: F-box_5 (PF18511)

Summary: F-box

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This is the Wikipedia entry entitled "F-box protein". More...

F-box protein Edit Wikipedia article

F-box linker domain
PDB 1fs2 EBI.jpg
Structure of the LRR linker domain of Skp2 in the Skp1-Skp2 complex.[1]
Symbol F-box
Pfam PF00646
Pfam clan CL0271
InterPro IPR001810
SCOP 1fs2

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.

Core components

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 position. 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 concert 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]


The F-box protein is a big superfamily in Eukaryotic cells like yeast, plant, human. The F-box protein has been found on cytoplasm and nucleus. But it's hard to precisely decide which organism organ in cell does the F-box protein locate because the number of F-box protein is so much.[5]


F-box proteins have also been associated with cellular functions such as signal transduction and regulation of the cell cycle.[6] In plants, many F-box proteins are represented in gene networks broadly regulated by microRNA-mediated gene silencing via RNA interference.[7] 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.[8] ACRE189/ACIF1 can regulate cell death and defense when the pathogen is recognized in the Tobacco and Tomato plant.[9]

In human cells, in high-iron condition, two iron atoms stabilise the F-Box FBXL5 and then the complex mediates the ubiquitination of IRP2.[10]


F-box protein as a protein can be regulated in different mechanisms. The regulation can happen in the F-box protein synthesis process, protein degradation process and association with SCF complex process. For example, in yeast, the F-box protein Met30 can be ubiquitinated in a cullin-dependent manner.[11][11]


  1. ^ Schulman BA, Carrano AC, Jeffrey PD, et al. (November 2000). "Insights into SCF ubiquitin ligases from the structure of the Skp1-Skp2 complex". Nature. 408 (6810): 381–6. doi:10.1038/35042620. PMID 11099048. 
  2. ^ Bai C, Sen P, Hofmann K, Ma L, Goebl M, Harper JW, Elledge SJ. "SKP1 connects cell cycle regulators to the ubiquitin proteolysis machinery through a novel motif, the F-box". Cell 86 263-74 1996.
  3. ^ Bai C, Sen P, Hofmann K, Ma L, Goebl M, Harper JW, Elledge SJ (July 1996). "SKP1 connects cell cycle regulators to the ubiquitin proteolysis machinery through a novel motif, the F-box". Cell. 86 (2): 263–74. doi:10.1016/S0092-8674(00)80098-7. PMID 8706131.
  4. ^ Kipreos ET, Pagano M (2000). "The F-box protein family". Genome Biol. 1 (5): REVIEWS3002. doi:10.1186/gb-2000-1-5-reviews3002. PMC 138887Freely accessible. PMID 11178263. 
  5. ^ Rajasekharan, Sathyanath; Kennedy, Timothy E (2013). "Protein family review The netrin protein family".
  6. ^ Craig KL, Tyers M (1999). "The F-box: a new motif for ubiquitin dependent proteolysis in cell cycle regulation and signal transduction". Prog. Biophys. Mol. Biol. 72 (3): 299–328. doi:10.1016/S0079-6107(99)00010-3. PMID 10581972. 
  7. ^ Jones-Rhoades MW, Bartel DP, Bartel B (2006). "MicroRNAS and their regulatory roles in plants". Annu Rev Plant Biol. 57: 19–53. doi:10.1146/annurev.arplant.57.032905.105218. PMID 16669754. 
  8. ^ Peng, Juan; Yu, Dashi; Wang, Liqun; Xie, Minmin; Yuan, Congying; Wang, Yu; Tang, Dongying; Zhao, Xiaoying; Liu, Xuanming (June 2012). "Arabidopsis F-box gene FOA1 involved in ABA signaling". Science China. Life Sciences. 55 (6): 497–506. doi:10.1007/s11427-012-4332-9. ISSN 1869-1889. PMID 22744179.
  9. ^ Ha, Van Den Burg; Tsitsigiannis, D. I.; Rowland, O; Lo, J; Rallapalli, G; Maclean, D; Takken, F. L.; Jones, J. D. (2008). "The F-box protein ACRE189/ACIF1 regulates cell death and defense responses activated during pathogen recognition in tobacco and tomato". Plant Cell. 20 (3): 697.
  10. ^ Moroishi, T; Nishiyama, M; Takeda, Y; Iwai, K; Nakayama, K. I. (2011). "The FBXL5-IRP2 axis is integral to control of iron metabolism in vivo". Cell Metabolism. 14 (3): 339.
  11. ^ Kaiser, Peter; Su, Ning-Yuan; Yen, James L.; Ouni, Ikram; Flick, Karin (2006-08-08). "The yeast ubiquitin ligase SCFMet30: connecting environmental and intracellular conditions to cell division". Cell Division. 1: 16. doi:10.1186/1747-1028-1-16. ISSN 1747-1028.

Further reading

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This page is based on a Wikipedia article. The text is available under the Creative Commons Attribution/Share-Alike License.

This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.

F-box Provide feedback

Jasmonates are a family of plant hormones that regulate plant growth, development and responses to stress. COI1 is an F-box protein that functions as the substrate-recruiting module of the Skp1-Cul1-F-box protein (SCF) ubiquitin E3 ligase complex. The role of COI1-mediated JAZ degradation in jasmonate (JA) signaling is analogous to auxin signaling through the receptor F-box protein transport inhibitor response 1 (TIR1) , which promotes hormone-dependent turnover of the AUX/IAA transcriptional repressors. The crystal structure of COI1 reveals a TIR1-like overall architecture, with an N-terminal tri-helical F-box motif bound to ASK1 and a C-terminal horseshoe-shaped solenoid domain formed by 18 tandem leucine-rich repeats. This entry represents the N-terminal F-box domain which is also found in other auxin signaling f-box proteins such as AFB1, AFB2 and AFB3 [1].

Literature references

  1. Sheard LB, Tan X, Mao H, Withers J, Ben-Nissan G, Hinds TR, Kobayashi Y, Hsu FF, Sharon M, Browse J, He SY, Rizo J, Howe GA, Zheng N;, Nature. 2010;468:400-405.: Jasmonate perception by inositol-phosphate-potentiated COI1-JAZ co-receptor. PUBMED:20927106 EPMC:20927106

Internal database links

This tab holds annotation information from the InterPro database.

No InterPro data for this Pfam family.

Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

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Pfam Clan

This family is a member of clan F-box (CL0271), which has the following description:

This clan includes classical F-boxes and the PRANC domain found in pox ankyrin proteins.

The clan contains the following 7 members:

Elongin_A F-box F-box-like F-box-like_2 F-box_4 F-box_5 PRANC


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Curation and family details

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This family is new in this Pfam release.

Seed source: ECOD:EUF04885
Previous IDs: none
Type: Domain
Sequence Ontology: SO:0000417
Author: El-Gebali S
Number in seed: 37
Number in full: 990
Average length of the domain: 41.40 aa
Average identity of full alignment: 40 %
Average coverage of the sequence by the domain: 6.99 %

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HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 45638612 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 25.5 25.5
Trusted cut-off 25.5 25.5
Noise cut-off 25.4 25.4
Model length: 42
Family (HMM) version: 1
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Species distribution

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Archea Archea Eukaryota Eukaryota
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Viruses Viruses Unclassified Unclassified
Viroids Viroids Unclassified sequence Unclassified sequence


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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the F-box_5 domain has been found. There are 24 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein sequence.

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