Proteinase inhibitor I25, cystatin

Crystal structure of an immunomodulatory salivary cystatin from the soft tick Ornithodoros moubata from PDB entry 3L0R.[1]
Symbol Prot_inh_cystat
Pfam PF00031
Pfam clan CL0121
InterPro IPR000010

The cystatins are a family of cysteine protease inhibitors which share a sequence homology and a common tertiary structure of an alpha helix lying on top of an anti-parallel beta sheet. The family is subdivided as described below.

Cystatins show similarity to fetuins, kininogens, histidine-rich glycoproteins and cystatin-related proteins.[2][3][4] Cystatins mainly inhibit peptidase enzymes (another term for proteases) belonging to peptidase families C1 (papain family) and C13 (legumain family). They are known to mis-fold to form amyloid deposits and are implicated in several diseases.


The cystatin family includes:

Human cystatins

Plant cystatins

van Wyk et al found some 19 different cystatins similar to oryzacystatin-I in the soybean along with related cysteine proteases.[6]

Membrane permeability

Chicken cystatin quickly passed the membrane of MCF-10A neo T cells and inhibited cathepsin B when it was acylated with fatty acyl residues of 6-18 carbon atoms.[7]

See also


  1. Salát, Jiří; Paesen, Guido C.; Řezáčová, Pavlína; Kotsyfakis, Michalis; Kovářová, Zuzana; Šanda, Miloslav; Majtán, Juraj; Grunclová, Lenka; Horká, Helena; Andersen, John F.; Brynda, Jiří; Horn, Martin; Nunn, Miles A.; Kopáček, Petr; Kopecký, Jan; Mareš, Michael (2010). "Crystal structure and functional characterization of an immunomodulatory salivary cystatin from the soft tick Ornithodoros moubata". Biochemical Journal. 429 (1): 103–12. doi:10.1042/BJ20100280. PMC 3523712Freely accessible. PMID 20545626.; rendered with PyMOL
  2. Rawlings, Neil D.; Barrett, Alan J. (1990). "Evolution of proteins of the cystatin superfamily". Journal of Molecular Evolution. 30 (1): 60–71. doi:10.1007/BF02102453. PMID 2107324.
  3. Abrahamson, Magnus; Alvarez-Fernandez, Marcia; Nathanson, Carl-Michael (2003). "Cystatins". Biochemical Society Symposium. 70 (70): 179–99. doi:10.1042/bss0700179. PMID 14587292.
  4. Turk, Vito; Bode, Wolfram (1991). "The cystatins: Protein inhibitors of cysteine proteinases". FEBS Letters. 285 (2): 213–9. doi:10.1016/0014-5793(91)80804-C. PMID 1855589.
  5. Machleidt, Werner; Borchart, Ursula; Fritz, Hans; Brzin, Jože; Ritonja, Anka; Turk, Vito (1983). "Protein Inhibitors of Cysteine Proteinases. II. Primary Structure of Stefin, a Cytosolic Protein Inhibitor of Cysteine Proteinases from Human Polymorphonuclear Granulocytes". Hoppe-Seyler's Zeitschrift für physiologische Chemie. 364 (11): 1481–6. doi:10.1515/bchm2.1983.364.2.1481. PMID 6689312.
  6. van Wyk, Stefan George; Du Plessis, Magdeleen; Cullis, Christoper Ashley; Kunert, Karl Josef; Vorster, Barend Juan (2014). "Cysteine protease and cystatin expression and activity during soybean nodule development and senescence". BMC Plant Biology. 14: 294. doi:10.1186/s12870-014-0294-3. PMC 4243279Freely accessible. PMID 25404209.
  7. Kočevar, Nina; Obermajer, Nataša; Kreft, Samo (2008). "Membrane Permeability of Acylated Cystatin Depends on the Fatty Acyl Chain Length". Chemical Biology & Drug Design. 72 (3): 217–24. doi:10.1111/j.1747-0285.2008.00693.x. PMID 18702630.

Further reading

  • Lee, Chunsik; Bongcam-Rudloff, Erik; Sollner, Christian; Jahnen-Dechent, Willi; Claesson-Welsh, Lena (2009). "Type 3 cystatins; fetuins, kininogen and histidine-rich glycoprotein". Frontiers in Bioscience. 14 (14): 2911–22. doi:10.2741/3422. PMID 19273244. 

External links

This article incorporates text from the public domain Pfam and InterPro IPR000010

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