Serine/threonine-protein kinase 4 is an
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
that in humans is encoded by the ''STK4''
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 b ...
.
Function
The protein encoded by this gene is a
cytoplasmic
In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The ...
kinase that is structurally similar to the yeast Ste20p (sterile 20 protein) kinase, which acts upstream of the stress-induced
mitogen-activated protein kinase
A mitogen-activated protein kinase (MAPK or MAP kinase) is a type of protein kinase that is specific to the amino acids serine and threonine (i.e., a serine/threonine-specific protein kinase). MAPKs are involved in directing cellular response ...
(MAPK) cascade. The encoded protein can
phosphorylate
In chemistry, phosphorylation is the attachment of a phosphate group to a molecule or an ion. This process and its inverse, dephosphorylation, are common in biology and could be driven by natural selection. Text was copied from this source, ...
myelin
Myelin is a lipid-rich material that surrounds nerve cell axons (the nervous system's "wires") to insulate them and increase the rate at which electrical impulses (called action potentials) are passed along the axon. The myelinated axon can ...
basic protein and undergoes
autophosphorylation
Autophosphorylation is a type of post-translational modification of proteins. It is generally defined as the phosphorylation of the kinase by itself. In eukaryotes, this process occurs by the addition of a phosphate group to serine, threonine o ...
. A
caspase
Caspases (cysteine-aspartic proteases, cysteine aspartases or cysteine-dependent aspartate-directed proteases) are a family of protease enzymes playing essential roles in programmed cell death. They are named caspases due to their specific cyste ...
-cleaved fragment of the encoded protein has been shown to be capable of phosphorylating
histone H2B
Histone H2B is one of the 5 main histone proteins involved in the structure of chromatin in eukaryotic cells. Featuring a main globular domain and long N-terminal and C-terminal tails, H2B is involved with the structure of the nucleosomes.
S ...
. The particular phosphorylation catalyzed by this protein has been correlated with
apoptosis
Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes ( morphology) and death. These changes in ...
, and it's possible that this protein induces the
chromatin condensation
Prophase () is the first stage of cell division in both mitosis and meiosis. Beginning after interphase, DNA has already been replicated when the cell enters prophase. The main occurrences in prophase are the condensation of the chromatin reti ...
observed in this process.
Interactions
STK4 has been shown to
interact
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with
PRKRIR
52 kDa repressor of the inhibitor of the protein kinase is an enzyme that in humans is encoded by the ''PRKRIR'' gene.
Interactions
PRKRIR has been shown to interact with STK4 and DNAJC3
DnaJ homolog subfamily C member 3 is a protein that in hu ...
.
STK4 has also been shown to prevent, through Yap1 coactivator modulation, haematological tumor cell apoptosis.
References
Further reading
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EC 2.7.11
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