The heat shock protein Hsp20 family, also known as small heat shock proteins (sHSPs), is a
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
of
heat shock proteins.
Prokaryotic and eukaryotic organisms respond to
heat shock or other
environmental stress
Stress, either physiological, biological or psychological, is an organism's response to a stressor such as an environmental condition. Stress is the body's method of reacting to a condition such as a threat, challenge or physical and psych ...
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, 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 the protein is ...
, 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
Heat shock protein 27 (Hsp27) also known as heat shock protein beta-1 (HSPB1) is a protein that in humans is encoded by the ''HSPB1'' gene.
Hsp27 is a chaperone of the sHsp (small heat shock protein) group among α-crystallin, Hsp20, and others. ...
*
HSPB2
*
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 a ...
)
*HSPB5 (
CRYAB
Alpha-crystallin B chain is a protein that in humans is encoded by the ''CRYAB'' gene. It is part of the small heat shock protein family and functions as molecular chaperone that primarily binds misfolded proteins to prevent protein aggregation, a ...
)
*
HSPB6
Heat shock protein beta-6 (HSPB6) is a protein that in humans is encoded by the ''HSPB6'' gene.
HSPB6 is a 17-kDa member of the heat shock family of proteins. HSPB6 was first identified in 1994 when it was isolated from rat and human skeletal mus ...
*
HSPB7
Heat Shock Protein Family B (small) member 7 (HSPB7) in humans is a protein encoded by a gene of the same name with four exons that is located on chromosome 1p36.13.,. HSPB7 contains 170 amino acids and has a Molecular mass, molecular weight of 18 ...
*
HSPB8
Heat shock protein beta-8 is a protein that in humans is encoded by the ''HSPB8'' gene.
Interactions
HSPB8 has been shown to interact with:
* HSPB2, and
* Hsp27.
Clinical importance
Mutations in this gene have been associated with an autosom ...
*
HSPB9
*
HSPB10
References
{{InterPro content, IPR002068
Heat shock proteins