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167  structures 2966  species 0  interactions 15830  sequences 408  architectures

Clan: Cystatin (CL0121)


Cystatin-like superfamily Add an annotation

This superfamily includes cystatins and cathelicidins [1]. The cystatin superfamily comprises cysteine protease inhibitors that play key regulatory roles in protein degradation processes. The progenitor of this superfamily was most probably intracellular and lacked a signal peptide and disulfide bridges, much like the extant Giardia cystatin. A primordial gene duplication produced two ancestral eukaryotic lineages, cystatins and stefins. Stefins - included in Pfam:PF00031 - remain encoded by a single or a small number of genes throughout the eukaryotes, whereas the cystatins have undergone a more complex and dynamic evolution through numerous gene and domain duplications [2].

This clan contains 13 families and the total number of domains in the clan is 15830. The clan was built by A Bateman.

Literature references

  1. Murzin AG; , J Mol Biol 1993;230:689-694.: Sweet-tasting protein monellin is related to the cystatin family of thiol proteinase inhibitors. PUBMED:8464079 EPMC:8464079
  2. Kordis D, Turk V;, BMC Evol Biol. 2009;9:266.: Phylogenomic analysis of the cystatin superfamily in eukaryotes and prokaryotes. PUBMED:19919722 EPMC:19919722


This clan contains the following 13 member families:

Cathelicidins Cystatin DUF3889 DUF5590 FTP Latexin Monellin PP1 Spp-24 SQAPI Staphopain_pro YebF YPEB

External database links

Domain organisation

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

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

Pfam family Num. domains Alignment
Cystatin (PF00031) 6502 (41.1%) View
FTP (PF07504) 3846 (24.3%) View
SQAPI (PF16845) 2372 (15.0%) View
YPEB (PF14620) 747 (4.7%) View
Cathelicidins (PF00666) 603 (3.8%) View
DUF5590 (PF17881) 595 (3.8%) View
Latexin (PF06907) 476 (3.0%) View
DUF3889 (PF13028) 307 (1.9%) View
Spp-24 (PF07448) 271 (1.7%) View
YebF (PF13995) 62 (0.4%) View
PP1 (PF07430) 42 (0.3%) View
Staphopain_pro (PF14731) 7 (0.0%) View
Monellin (PF09200) 0 (0.0%) View
Total: 13 Total: 15830 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.

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