Powering down the Pfam website
On October 5th, we began redirecting traffic from Pfam (pfam.xfam.org) to InterPro (www.ebi.ac.uk/interpro). The Pfam website will remain available at pfam-legacy.xfam.org until January 2023, when it will be decommissioned. You can read more about the sunset period in our blog post.

Please note: this site relies heavily on the use of javascript. Without a javascript-enabled browser, this site will not function correctly. Please enable javascript and reload the page, or switch to a different browser.
1593  structures 3316  species 0  interactions 71888  sequences 2468  architectures

Clan: Trefoil (CL0066)


Beta-trefoil superfamily Add an annotation

This family corresponds to a large set of related beta-trefoil proteins [1]. The beta-trefoil is formed by six two-stranded hairpins [2]. Three of these form a barrel structure and the other three are in a triangular array that caps the barrel. The arrangement of the secondary structures gives the molecules a pseudo 3-fold axis.

This clan contains 23 families and the total number of domains in the clan is 71888. The clan was built by A Bateman.

Literature references

  1. Ponting CP, Russell RB; , J Mol Biol 2000;302:1041-1047.: Identification of distant homologues of fibroblast growth factors suggests a common ancestor for all beta-trefoil proteins. PUBMED:11183773 EPMC:11183773
  2. Murzin AG, Lesk AM, Chothia C; , J Mol Biol 1992;223:531-543.: beta-Trefoil fold. Patterns of structure and sequence in the Kunitz inhibitors interleukins-1 beta and 1 alpha and fibroblast growth factors. PUBMED:1738162 EPMC:1738162


This clan contains the following 23 member families:

AbfB Agglutinin Agglutinin_C Botulinum_HA-17 BTD CDtoxinA DUF569 Fascin FGF FRG1 IL1 IL33 Inhibitor_I48 Inhibitor_I66 Ins145_P3_rec Kunitz_legume Lectin_C_term Lipoprotein_11 MIR NTNH_C Ricin_B_lectin RicinB_lectin_2 Toxin_R_bind_C

External database links

Domain organisation

Below is a listing of the unique domain organisations or architectures from this clan. More...

Loading domain graphics...


The table below shows the number of occurrences of each domain throughout the sequence database. More...

Pfam family Num. domains Alignment
Ricin_B_lectin (PF00652) 19009 (26.4%) View
RicinB_lectin_2 (PF14200) 12801 (17.8%) View
MIR (PF02815) 9884 (13.7%) View
FGF (PF00167) 8734 (12.1%) View
Ins145_P3_rec (PF08709) 5170 (7.2%) View
Fascin (PF06268) 3763 (5.2%) View
AbfB (PF05270) 2183 (3.0%) View
BTD (PF09270) 1923 (2.7%) View
IL1 (PF00340) 1857 (2.6%) View
Kunitz_legume (PF00197) 1830 (2.5%) View
DUF569 (PF04601) 1540 (2.1%) View
FRG1 (PF06229) 1399 (1.9%) View
Pfam family Num. domains Alignment
Agglutinin (PF07468) 790 (1.1%) View
Inhibitor_I66 (PF16850) 358 (0.5%) View
IL33 (PF15095) 220 (0.3%) View
Lipoprotein_11 (PF03260) 143 (0.2%) View
CDtoxinA (PF03498) 109 (0.2%) View
Inhibitor_I48 (PF10467) 83 (0.1%) View
Agglutinin_C (PF18021) 65 (0.1%) View
Botulinum_HA-17 (PF05588) 9 (0.0%) View
Lectin_C_term (PF18022) 6 (0.0%) View
NTNH_C (PF08470) 6 (0.0%) View
Toxin_R_bind_C (PF07951) 6 (0.0%) View
Total: 23 Total: 71888 Clan alignment

Please note: Clan alignments can be very large and can cause problems for some browsers. Read the note above before viewing.

Family relationships

This diagram shows the relationships between members of this clan. More...

Species distribution

Tree controls


This tree shows the occurrence of the domains in this clan across different species. More...



For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the MSD group, to allow us to map Pfam domains onto UniProt three-dimensional structures. The table below shows the mapping between the Pfam families in this clan, the corresponding UniProt entries, and the region of the three-dimensional structures that are available for that sequence.

Loading structure mapping...