15 kDa selenoprotein 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 ''SEP15''
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 ...
.
Two alternatively spliced transcript variants encoding distinct
isoforms
A protein isoform, or "protein variant", is a member of a set of highly similar proteins that originate from a single gene or gene family and are the result of genetic differences. While many perform the same or similar biological roles, some isof ...
have been found for this gene.
Function
This gene encodes a
selenoprotein, which contains a
selenocysteine
Selenocysteine (symbol Sec or U, in older publications also as Se-Cys) is the 21st proteinogenic amino acid. Selenoproteins contain selenocysteine residues. Selenocysteine is an analogue of the more common cysteine with selenium in place of the s ...
(Sec) residue at its active site. The selenocysteine is encoded by the
UGA codon
The genetic code is the set of rules used by living cells to translate information encoded within genetic material ( DNA or RNA sequences of nucleotide triplets, or codons) into proteins. Translation is accomplished by the ribosome, which links ...
that normally signals translation termination. The 3' UTR of selenoprotein genes have a common
stem-loop
Stem-loop intramolecular base pairing is a pattern that can occur in single-stranded RNA. The structure is also known as a hairpin or hairpin loop. It occurs when two regions of the same strand, usually complementary in nucleotide sequence when ...
structure, the sec insertion sequence (
SECIS
In biology, the SECIS element (SECIS: ''selenocysteine insertion sequence'') is an RNA element around 60 nucleotides in length that adopts a stem-loop structure. This structural motif (pattern of nucleotides) directs the cell to translate UGA ...
), that is necessary for the recognition of UGA as a Sec codon rather than as a stop signal. Studies in mouse suggest that this selenoprotein may have
redox
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction ...
function and may be involved in the quality control of
protein folding
Protein folding is the physical process by which a protein chain is translated to its native three-dimensional structure, typically a "folded" conformation by which the protein becomes biologically functional. Via an expeditious and reproduci ...
.
Clinical significance
This gene is localized on chromosome 1p31, a genetic locus commonly mutated or deleted in human cancers.
Protein domain
The protein this gene encodes for is often called Sep15 however in the case of
mice
A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...
, it is named SelM. This protein is a
selenoprotein only found in
eukaryotes
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...
. This domain has a
thioredoxin-like
domain
Domain may refer to:
Mathematics
*Domain of a function, the set of input values for which the (total) function is defined
**Domain of definition of a partial function
**Natural domain of a partial function
**Domain of holomorphy of a function
* Do ...
and a surface accessible
active site
In biology and biochemistry, the active site is the region of an enzyme where substrate molecules bind and undergo a chemical reaction. The active site consists of amino acid residues that form temporary bonds with the substrate (binding site) a ...
redox
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction ...
motif
Motif may refer to:
General concepts
* Motif (chess composition), an element of a move in the consideration of its purpose
* Motif (folkloristics), a recurring element that creates recognizable patterns in folklore and folk-art traditions
* Moti ...
.
This suggests that they function as thiol-
disulfide isomerases involved in disulfide
bond
Bond or bonds may refer to:
Common meanings
* Bond (finance), a type of debt security
* Bail bond, a commercial third-party guarantor of surety bonds in the United States
* Chemical bond, the attraction of atoms, ions or molecules to form chemical ...
formation in the
endoplasmic reticulum
The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ( ...
.
Function
Recent studies have shown in mice, where the SEP15 gene has been
silenced the mice subsequently became deficient in SEP15 and were able to inhibit the development of colorectal cancer.
Structure
The particular structure has an alpha/beta central domain which is actually made up of three
alpha helices and a mixed parallel/anti-parallel four-stranded
beta-sheet.
References
Further reading
*
*
*
*
*
*
*
*
*
*
*
Selenoproteins
{{protein-stub