BPI fold containing family B, member 3 (BPIFB3) is a protein that in humans is encoded by the ''BPIFB3'' gene. Two variants have been detected in humans.

Superfamily

BPIFB3 is a member of a BPI fold

protein superfamily A protein superfamily is the largest grouping (clade) of proteins for which common ancestry can be inferred (see homology (biology), homology). Usually this common ancestry is inferred from structural alignment and mechanistic similarity, even if n ...

defined by the presence of the bactericidal/permeability-increasing protein fold (BPI fold) which is formed by two similar domains in a "boomerang" shape. This superfamily is also known as the BPI/LBP/PLUNC family or the BPI/ LPB/ CETP family. The BPI fold creates apolar binding pockets that can interact with hydrophobic and amphipathic molecules, such as the acyl carbon chains of lipopolysaccharide found on Gram-negative bacteria, but members of this family may have many other functions. BPIFfamily-BPIFB3

Genes for the BPI/LBP/PLUNC superfamily are found in all vertebrate species, including distant homologs in non-vertebrate species such as insects, mollusks, and roundworms. Within that broad grouping is the BPIF gene family whose members encode the BPI fold

structural motif In a polymer, chain-like biological molecule, such as a protein or nucleic acid, a structural motif is a common Biomolecular structure#Tertiary structure, three-dimensional structure that appears in a variety of different, evolutionarily unrel ...

and are found clustered on a single chromosome, e.g., Chromosome 20 in humans, Chromosome 2 in mouse, Chromosome 3 in rat, Chromosome 17 in pig, Chromosome 13 in cow. The BPIF gene family is split into two groupings, BPIFA and BPIFB. In humans, BIPFA consists of 3 protein encoding genes ''

BPIFA1 BPI fold containing family A, member 1 (BPIFA1), also known as Palate, lung, and nasal epithelium clone (PLUNC), is a protein that in humans is encoded by the ''BPIFA1'' gene. It was also formerly known as "Secretory protein in upper respiratory ...

'', '' BPIFA2'', '' BPIFA3'', and 1 pseudogene '' BPIFA4P''; while BPIFB consists of 5 protein encoding genes '' BPIFB1'', ''

BPIFB2 BPI fold-containing family B, member 2, (BPIFB2) also known as bactericidal/permeability-increasing protein-like 1, (BPI-like 1) is a protein that in humans is encoded by the ''BPIFB2'' gene. Superfamily BPIFB2 is a member of a BPI fold prote ...

'', ''BPIFB3'', '' BPIFB4'', '' BPIFB6'' and 2 pseudogenes '' BPIFB5P'', ''

BPIFB9P Vomeromodulin is a non-human protein also known as BPI fold containing family B, member 9 (BPIFB9) in the rat encoded by the ''Bpifb9/RYF3'' gene, and as BPI fold containing family B, member 9A (BPIFB9A) encoded by the ''Bpifb9a'' gene in the m ...

''. What appears as pseudogenes in humans may appear as fully functional genes in other species. ''BPIFB3'' was first directly identified in a screen of rat olfactory epithelium as ''RYA3'' and was recognized to be a member of the BPI fold superfamily. In humans, it was formerly known as "Long palate, lung and nasal epithelium carcinoma-associated protein 3" encoded by the ''LPLUNC3'' gene. The ''BPIFB3'' gene is found with other members of the BPIF gene family in a cluster on chromosome 20.

Function

BPIFB3/RYA3 is highly expressed in olfactory epithelium and the tongue, within the cytoplasm of cells, and is thought to be similar to an

odorant binding protein Odorant-binding proteins (OBPs) are small (10 to 30 kDa) soluble proteins secreted by auxiliary cells surrounding olfactory receptor neurons, including the nasal mucus of many vertebrate species and in the sensillar lymph of chemosensory sensilla o ...

which presents odorant molecules to chemical odorant receptor molecules. Like other BPI-fold family members involved in defense from infection, BPIFB3 may be involved in responses to viral infections such as the enteroviruses coxsackievirus B and poliovirus in epithelial and endothelial tissue. Its cytoplasmic location appears to be localized to the

endoplasmic reticulum The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ( ...

(ER) and influences the replication of coxsackievirus B; when BPIFB3 is knocked out in experimental systems coxsackievirus B replication dramatically increases. It has been within observed in the ER to be physically associated with another family member, BPIFB6, and modulation of either of these two proteins can enhance or suppress enteroviral release from cells.

References

External links

* {{UCSC gene info, BPIFB3 Human proteins Genes Genes on human chromosome 20