Cystatin

Available protein structures:
PDB	PDB: 1a67 PDB: 1a90 PDB: 1cew PDB: 1cyu PDB: 1cyv PDB: 1dvc PDB: 1dvd PDB: 1eqk PDB: 1g96 PDB: 1gd3 IPR000010 PF00031 (ECOD; PDBsum)
AlphaFold	IPR000010; PF00031;

Proteinase inhibitor I25, cystatin
Proteinase inhibitor I25, cystatin
	Crystal structure of an immunomodulatory salivary cystatin from the soft tick Ornithodoros moubata from PDB entry 3L0R.
Identifiers
Symbol	Prot_inh_cystat
Pfam	PF00031
Pfam clan	CL0121
InterPro	IPR000010
SMART	SM00043
PROSITE	PDOC00259
PDB
Available protein structures:
PDB	PDB: 1a67 PDB: 1a90 PDB: 1cew PDB: 1cyu PDB: 1cyv PDB: 1dvc PDB: 1dvd PDB: 1eqk PDB: 1g96 PDB: 1gd3 IPR000010 PF00031 (ECOD; PDBsum)
AlphaFold	IPR000010; PF00031;

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. 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.