Hsp20
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The heat shock protein Hsp20 family, also known as small heat shock proteins (sHSPs), is a
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
of
heat shock proteins Heat shock proteins (HSPs) are a family of proteins produced by cells in response to exposure to stressful conditions. They were first described in relation to heat shock, but are now known to also be expressed during other stresses including ex ...
. Prokaryotic and eukaryotic organisms respond to
heat shock The heat shock response (HSR) is a cell stress response that increases the number of molecular chaperones to combat the negative effects on proteins caused by stressors such as increased temperatures, oxidative stress, and heavy metals. In a norm ...
or other environmental stress by inducing the synthesis of proteins collectively known as heat-shock proteins (hsp). Amongst them is a family of proteins with an average molecular weight of 20 kDa, known as the hsp20 proteins. These seem to act as protein chaperones that can protect other proteins against heat-induced denaturation and aggregation. Hsp20 proteins seem to form large heterooligomeric aggregates. Structurally, this family is characterised by the presence of a conserved
C-terminal domain The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, carboxy tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein or polypeptide), terminated by a free carboxyl group (-COOH). When t ...
, alpha-crystallin domain, of about 100 residues. Recently, small heat shock proteins (sHSPs) were found in marine viruses ( cyanophages).


Function and regulation

Hsp20, like all heat shock proteins, is in abundance when cells are under stressed conditions. Hsp20 is known to be expressed in many human tissues, including the brain and heart. Hsp20 has been studied extensively in cardiac myocytes and is known to act as a chaperon protein, binding to protein kinase 1 (PDK1) and allowing its nuclear transport. In addition, the phosphorylation of hsp20 has been shown to effect the structure of cells cytoskeletons. Due to hsp20 commonly forming dimers with itself when heated, its function of chaperoning can be greatly affected.


Human small heat shock proteins

* HSPB1 *
HSPB2 Heat shock protein beta-2 is a protein that in humans is encoded by the ''HSPB2'' gene. Interactions HSPB2 has been shown to interact with: * CRYAB, * HSPB8, * Myotonic dystrophy protein kinase and * TRAF6 TRAF6 is a TRAF human protei ...
* HSPB3 *HSPB4 (
CRYAA Alpha-crystallin A chain is a protein that in humans is encoded by the ''CRYAA'' gene. Crystallins are separated into two classes: taxon-specific, or enzyme, and ubiquitous. The latter class constitutes the major proteins of vertebrate eye lens ...
) *HSPB5 ( CRYAB) * HSPB6 * HSPB7 *
HSPB8 Heat shock protein beta-8 is a protein that in humans is encoded by the ''HSPB8'' gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that i ...
* HSPB9 * HSPB10


References

{{InterPro content, IPR002068 Heat shock proteins