Cystatin-A is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
that in humans is encoded by the ''CSTA''
gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
.
The
cystatin
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 sho ...
superfamily encompasses proteins that contain multiple cystatin-like sequences. Some of the members are active cysteine protease inhibitors, while others have lost or perhaps never acquired this inhibitory activity. There are three inhibitory families in the superfamily, including the type 1 cystatins (stefins), type 2 cystatins, and
kininogens Kininogens are precursor proteins for kinins, biologically active polypeptides involved in blood coagulation, vasodilation, smooth muscle contraction, inflammatory regulation, and the regulation of the cardiovascular and renal systems.
Types o ...
. This gene encodes a stefin that functions as a cysteine protease inhibitor, forming tight complexes with
papain
Papain, also known as papaya proteinase I, is a cysteine protease () enzyme present in papaya (''Carica papaya'') and mountain papaya (''Vasconcellea cundinamarcensis''). It is the namesake member of the papain-like protease family.
It has wide ...
and the cathepsins B, H, and L. The protein is one of the precursor proteins of
cornified cell envelope in
keratinocytes
Keratinocytes are the primary type of cell found in the epidermis, the outermost layer of the skin. In humans, they constitute 90% of epidermal skin cells.
Basal cells in the basal layer (''stratum basale'') of the skin are sometimes referred ...
and plays a role in epidermal development and maintenance. Stefins have been proposed as prognostic and diagnostic tools for cancer.
Interactions
Cystatin A has been shown to
interact
Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization using innovative strategies to advocate for the legal and human rights of children with intersex traits. The organizati ...
with
Cathepsin B
Cathepsin B belongs to a family of lysosomal cysteine proteases known as the cysteine cathepsins and plays an important role in intracellular proteolysis. In humans, cathepsin B is encoded by the ''CTSB'' gene. Cathepsin B is upregulated in cert ...
and
CTSL1
Cathepsin L1 is a protein that in humans is encoded by the ''CTSL1'' gene. The protein is a cysteine cathepsin, a lysosomal cysteine protease that plays a major role in intracellular protein catabolism.
Function
Cathepsin L1 is a member of the ...
.
See also
* Peptide Transporter Carbon Starvation (cstA) Family
References
Further reading
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External links
Cystatin: a protein that flips out!
QUite Interesting PDB Structure article a
PDBe
* The MEROPS
MEROPS is an online database for peptidases (also known as proteases, proteinases and proteolytic enzymes) and their inhibitors. The classification scheme for peptidases was published by Rawlings & Barrett in 1993, and that for protein inhibitor ...
online database for peptidases and their inhibitors
I25.001
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