Pentraxins
Encyclopedia
Pentraxins, also known as pentaxins, are an evolutionary conserved family of proteins characterised by containing a pentraxin protein domain
. Proteins of the pentraxin family are involved in acute immunological responses. They are a class of pattern recognition receptor
s (PRRs).
dependent ligand
binding and a distinctive flattened β-jellyroll structure similar to that of the legume lectins. The name "pentraxin" is derived from the Greek word for five (penta) and berries (ragos) relating to the radial symmetry of five monomer
s forming a ring approximately 95Å across and 35Å deep observed in the first members of this family to be identified. The "short" pentraxins include Serum Amyloid P component
(SAP) and C reactive protein (CRP). The "long" pentraxins include PTX3
(a cytokine modulated molecule) and several neuronal pentraxins.
(or TSG-14) protein is a cytokine-induced protein that is homologous to CRPs and SAPs, but its function has not yet been determined.
is expressed during acute phase response to tissue injury or inflammation in mammals. The protein resembles antibody and performs several functions associated with host defence: it promotes agglutination, bacterial capsular swelling and phagocytosis, and activates the classical complement pathway through its calcium-dependent binding to phosphocholine. CRPs have also been sequenced in an invertebrate, Limulus polyphemus (Atlantic horseshoe crab), where they are a normal constituent of the hemolymph.
is a vertebrate protein that is identical to tissue forms of amyloid P component. It is found in all types of amyloid deposits, in glomerular basement menbrane and in elastic fibres in blood vessels. SAP binds to various lipoprotein ligands in a calcium-dependent manner, and it has been suggested that, in mammals, this may have important implications in atherosclerosis and amyloidosis.
) and II (NPTXII
). NPTXI and NPTXII are homologous and can exist within one species. It is suggested that both proteins mediate the uptake of synaptic macromolecules and play a role in synaptic plasticity. Apexin, a sperm acrosomal protein, is a homologue of NPTXII found in Cavia porcellus (Guinea pig).
Protein domain
A protein domain is a part of protein sequence and structure that can evolve, function, and exist independently of the rest of the protein chain. Each domain forms a compact three-dimensional structure and often can be independently stable and folded. Many proteins consist of several structural...
. Proteins of the pentraxin family are involved in acute immunological responses. They are a class of pattern recognition receptor
Pattern recognition receptor
Pattern recognition receptors are a primitive part of the immune system. They are proteins expressed by cells of the innate immune system to identify pathogen-associated molecular patterns , which are associated with microbial pathogens or cellular stress, as well as damage-associated molecular...
s (PRRs).
Structure
Pentraxins are characterised by calciumCalcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
dependent ligand
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
binding and a distinctive flattened β-jellyroll structure similar to that of the legume lectins. The name "pentraxin" is derived from the Greek word for five (penta) and berries (ragos) relating to the radial symmetry of five monomer
Monomer
A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...
s forming a ring approximately 95Å across and 35Å deep observed in the first members of this family to be identified. The "short" pentraxins include Serum Amyloid P component
Serum Amyloid P component
Amyloid P component, serum is the identical serum form of amyloid P component , a 25kDa pentameric protein first identified as the pentagonal constituent of in vivo pathological deposits called "amyloid"...
(SAP) and C reactive protein (CRP). The "long" pentraxins include PTX3
PTX3
Pentraxin-related protein PTX3 also known as TNF-inducible gene 14 protein is a protein that in humans is encoded by the PTX3 gene.Pentraxin 3 is a member of the pentraxin superfamily...
(a cytokine modulated molecule) and several neuronal pentraxins.
Family members
Three of the principal members of the pentraxin family are serum proteins: namely, C-reactive protein (CRP), serum amyloid P component protein (SAP), and female protein (FP). PTX3PTX3
Pentraxin-related protein PTX3 also known as TNF-inducible gene 14 protein is a protein that in humans is encoded by the PTX3 gene.Pentraxin 3 is a member of the pentraxin superfamily...
(or TSG-14) protein is a cytokine-induced protein that is homologous to CRPs and SAPs, but its function has not yet been determined.
C-reactive protein
C-reactive proteinC-reactive protein
C-reactive protein is a protein found in the blood, the levels of which rise in response to inflammation...
is expressed during acute phase response to tissue injury or inflammation in mammals. The protein resembles antibody and performs several functions associated with host defence: it promotes agglutination, bacterial capsular swelling and phagocytosis, and activates the classical complement pathway through its calcium-dependent binding to phosphocholine. CRPs have also been sequenced in an invertebrate, Limulus polyphemus (Atlantic horseshoe crab), where they are a normal constituent of the hemolymph.
Serum amyloid P component
Serum amyloid P componentSerum Amyloid P component
Amyloid P component, serum is the identical serum form of amyloid P component , a 25kDa pentameric protein first identified as the pentagonal constituent of in vivo pathological deposits called "amyloid"...
is a vertebrate protein that is identical to tissue forms of amyloid P component. It is found in all types of amyloid deposits, in glomerular basement menbrane and in elastic fibres in blood vessels. SAP binds to various lipoprotein ligands in a calcium-dependent manner, and it has been suggested that, in mammals, this may have important implications in atherosclerosis and amyloidosis.
Hamster female protein
Hamster female protein is a SAP homologue found in Mesocricetus auratus (Golden hamster). The concentration of this plasma protein is altered by sex steroids and stimuli that elicit an acute phase response.Nervous system
Pentraxin proteins expressed in the nervous system are neural pentraxin I (NPTXINPTX1
Neuronal pentraxin-1 is a protein that in humans is encoded by the NPTX1 gene.- Function :NPTX1 is a member of the neuronal pentraxin gene family. Neuronal pentraxin 1 is similar to the rat NP1 gene which encodes a binding protein for the snake venom toxin taipoxin. Human NPTX1 mRNA is exclusively...
) and II (NPTXII
NPTX2
Neuronal pentraxin-2 is a protein that in humans is encoded by the NPTX2 gene.- Function :This gene encodes a member of the family of neuronal petraxins, synaptic proteins that are related to C-reactive protein. This protein is involved in excitatory synapse formation...
). NPTXI and NPTXII are homologous and can exist within one species. It is suggested that both proteins mediate the uptake of synaptic macromolecules and play a role in synaptic plasticity. Apexin, a sperm acrosomal protein, is a homologue of NPTXII found in Cavia porcellus (Guinea pig).
Human
Human genes encoding proteins that contain this domain include:- APCSSerum Amyloid P componentAmyloid P component, serum is the identical serum form of amyloid P component , a 25kDa pentameric protein first identified as the pentagonal constituent of in vivo pathological deposits called "amyloid"...
- CRPC-reactive proteinC-reactive protein is a protein found in the blood, the levels of which rise in response to inflammation...
- GPR144GPR144Probable G-protein coupled receptor 144 is a protein that in humans is encoded by the GPR144 gene.-Further reading:...
- NPTX1NPTX1Neuronal pentraxin-1 is a protein that in humans is encoded by the NPTX1 gene.- Function :NPTX1 is a member of the neuronal pentraxin gene family. Neuronal pentraxin 1 is similar to the rat NP1 gene which encodes a binding protein for the snake venom toxin taipoxin. Human NPTX1 mRNA is exclusively...
; NPTX2NPTX2Neuronal pentraxin-2 is a protein that in humans is encoded by the NPTX2 gene.- Function :This gene encodes a member of the family of neuronal petraxins, synaptic proteins that are related to C-reactive protein. This protein is involved in excitatory synapse formation...
; NPTXRNPTXRNeuronal pentraxin receptor is a protein that in humans is encoded by the NPTXR gene.-Further reading:... - PTX3PTX3Pentraxin-related protein PTX3 also known as TNF-inducible gene 14 protein is a protein that in humans is encoded by the PTX3 gene.Pentraxin 3 is a member of the pentraxin superfamily...
- SVEP1