Signal transducing adaptor proteins (STAPs) are

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

s that are accessory to main proteins in a

signal transduction Signal transduction is the process by which a chemical or physical signal is transmitted through a cell as a biochemical cascade, series of molecular events. Proteins responsible for detecting stimuli are generally termed receptor (biology), rece ...

pathway. Adaptor proteins contain a variety of protein-binding modules that link protein-binding partners together and facilitate the creation of larger signaling complexes. These proteins tend to lack any intrinsic enzymatic activity themselves, instead mediating specific protein–protein interactions that drive the formation of

protein complexes A protein complex or multiprotein complex is a group of two or more associated polypeptide chains. Protein complexes are distinct from multidomain enzymes, in which multiple catalytic domains are found in a single polypeptide chain. Protein c ...

. Examples of adaptor proteins include

MYD88 Myeloid differentiation primary response 88 (MYD88) is a protein that, in humans, is encoded by the ''MYD88'' gene. originally discovered in the laboratory of Dan A. Liebermann (Lord et al. Oncogene 1990) as a Myeloid differentiation primary resp ...

Grb2 Growth factor receptor-bound protein 2, also known as Grb2, is an adaptor protein involved in signal transduction/ cell communication. In humans, the GRB2 protein is encoded by the ''GRB2'' gene. The protein encoded by this gene binds recepto ...

and

SHC1 SHC-transforming protein 1 is a protein that in humans is encoded by the ''SHC1'' gene. SHC has been found to be important in the regulation of apoptosis and drug resistance in mammalian cells. SCOP A ( or ) was a poet as represented in Old ...

Signaling components

Much of the specificity of

depends on the recruitment of several signalling components such as

protein kinases A protein kinase is a kinase which selectively modifies other proteins by covalently adding phosphates to them (phosphorylation) as opposed to kinases which modify lipids, carbohydrates, or other molecules. Phosphorylation usually results in a fun ...

and G-protein

GTPase GTPases are a large family of hydrolase enzymes that bind to the nucleotide guanosine triphosphate (GTP) and hydrolyze it to guanosine diphosphate (GDP). The GTP binding and hydrolysis takes place in the highly conserved P-loop "G domain", a ...

s into short-lived active complexes in response to an activating signal such as a

growth factor A growth factor is a naturally occurring substance capable of stimulating cell proliferation, wound healing, and occasionally cellular differentiation. Usually it is a secreted protein or a steroid hormone. Growth factors are important for ...

binding to its

receptor Receptor may refer to: * Sensory receptor, in physiology, any neurite structure that, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and respond ...

Domains

Adaptor proteins usually contain several domains within their structure (e.g., Src homology 2 (SH2) and

SH3 domain The SRC Homology 3 Domain (or SH3 domain) is a small protein domain of about 60 amino acid residues. Initially, SH3 was described as a conserved sequence in the viral adaptor protein v-Crk. This domain is also present in the molecules of ph ...

s) that allow specific interactions with several other specific proteins. SH2 domains recognise specific amino acid sequences within proteins containing

phosphotyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a conditionally essential amino acid with a polar side group. The word "tyrosine" is f ...

residues and SH3 domains recognise

proline Proline (symbol Pro or P) is an organic acid classed as a proteinogenic amino acid (used in the biosynthesis of proteins), although it does not contain the amino group but is rather a secondary amine. The secondary amine nitrogen is in the p ...

-rich sequences within specific peptide sequence contexts of proteins. There are many other types of interaction domains found within adaptor and other signalling proteins that allow a rich diversity of specific and coordinated protein–protein interactions to occur within the cell during

Examples of adaptor proteins

Adaptor proteins include: * BCAR3 – Breast cancer anti-estrogen resistance protein 3 * CBL – Casitas B-lineage Lymphoma * FRS2 – Fibroblast growth factor receptor substrate 2 *

GAB2 GRB2-associated-binding protein 2 also known as GAB2 is a protein that in humans is encoded by the ''GAB2'' gene. GAB2 is a docking protein with a conserved, folded PH domain attached to the membrane and a large disordered region, which hosts in ...

– GRB2-associated binding protein 2 *

GRAP GRB2-related adapter protein is a protein that in humans is encoded by the ''GRAP'' gene. This gene encodes a member of the GRB2/Sem5 ('' C. elegans'' homolog)/Drk (''Drosophila'' homolog) family. This member functions as a cytoplasmic signaling ...

– GRB2-related adaptor protein *

GRAP2 GRB2-related adapter protein 2 also known as GRB2-related adaptor downstream of Shc (GADS) is a 37 kDa protein that in humans is encoded by the ''GRAP2'' gene. Function This gene encodes a member of the GRB2/Sem5/Drk family. This member is a ...

– GRB2-related adaptor protein 2 *

GRB2 Growth factor receptor-bound protein 2, also known as Grb2, is an adaptor protein involved in signal transduction/ cell communication. In humans, the GRB2 protein is encoded by the ''GRB2'' gene. The protein encoded by this gene binds recepto ...

– Growth factor receptor-bound protein 2 *

IRS1 Insulin receptor substrate 1 (IRS-1) is a signaling adapter protein that in humans is encoded by the ''IRS1'' gene. It is a 180 kDa protein with amino acid sequence of 1242 residues. It contains a single pleckstrin homology (PH) domain at the N-t ...

– Insulin receptor substrate 1 *

LDLRAP1 Low-density lipoprotein receptor adapter protein 1 is a protein that in humans is encoded by the ''LDLRAP1'' gene. The protein encoded by this gene is a cytosolic protein which contains a phosphotyrosine binding (PTB) domain. The PTB domain has ...

– low-density lipoprotein receptor adaptor protein 1 *

- Myeloid differentiation primary response gene 88 *

NCDN Neurochondrin (also known as its murine homologue, Norbin) is a protein that in humans is encoded by the ''NCDN'' gene. This gene encodes a leucine-rich cytoplasmic protein, which is highly similar to a mouse protein norbin that negatively regula ...

- Neurochondrin *

NCK1 Cytoplasmic protein NCK1 is a protein that in humans is encoded by the ''NCK1'' gene. Gene The Nck (non-catalytic region of tyrosine kinase adaptor protein 1) belongs to the adaptor family of proteins. The nck gene was initially isolated fro ...

– NCK adaptor protein 1 *

NCK2 Cytoplasmic protein NCK2 (also known as NCK-beta and Grb4) is a protein that in humans is encoded by the ''NCK2'' gene. Function NCK belongs to family of adaptor proteins. There are two mammalian NCK genes, NCK1 and NCK2. NCK1 is located in c ...

– NCK adaptor protein 2 *

NOS1AP Nitric oxide synthase 1 adaptor protein (NOS1AP) also known as carboxyl-terminal PDZ ligand of neuronal nitric oxide synthase protein (CAPON) is a protein that in humans is encoded by the ''NOS1AP'' gene. This gene encodes a cytosolic protein th ...

– nitric oxide synthase 1 (neuronal) adaptor protein *

PIK3AP1 Phosphoinositide 3-kinase adapter protein 1 is an enzyme that in humans is encoded by the ''PIK3AP1'' 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 nucle ...

– phosphoinositide-3-kinase adaptor protein 1 *

SH2B1 SH2B adapter protein 1 is a protein that in humans is encoded by the ''SH2B1'' gene. Interactions SH2B1 has been shown to interact with: * Grb2, * Insulin receptor, * Janus kinase 2, and * TrkA. Clinical significance Variations close ...

– SH2B adaptor protein 1 *

SH2B2 SH2B adapter protein 2 is a protein that in humans is encoded by the ''SH2B2'' gene. Function The protein encoded by this gene is expressed in B lymphocytes and contains pleckstrin homology and src homology 2 (SH2) domains. In Burkitt lymphoma ...

– SH2B adaptor protein 2 * SH2B3 – SH2B adaptor protein 3 * SH2D3A -SH2 domain containing 3A * SH2D3C – SH2 domain containing 3C * SNTA1 – Syntrophin, alpha 1 * SHB – Src homology 2 domain containing adaptor protein B * SLC4A1AP – solute carrier family 4 (anion exchanger), member 1, adaptor protein

Signaling components

Domains

Examples of adaptor proteins

See also

References

Further reading