BPI fold-containing family B, member 2, (BPIFB2) also known as bactericidal/permeability-increasing protein-like 1, (BPI-like 1) is a

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 ...

that in humans is encoded by the ''BPIFB2''

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 is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

Superfamily

BPIFB2 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 Cholesteryl ester transfer protein (CETP), also called plasma lipid transfer protein, is a plasma protein that facilitates the transport of cholesteryl esters and triglycerides between the lipoproteins. It collects triglycerides from very-low- ...

family. The BPI fold creates apolar binding pockets that can interact with hydrophobic and

amphipathic In chemistry, an amphiphile (), or amphipath, is a chemical compound possessing both hydrophilic (''water-loving'', polar) and lipophilic (''fat-loving'', nonpolar) properties. Such a compound is called amphiphilic or amphipathic. Amphiphilic c ...

molecules, such as the acyl carbon chains of

lipopolysaccharide Lipopolysaccharide (LPS), now more commonly known as endotoxin, is a collective term for components of the outermost membrane of the cell envelope of gram-negative bacteria, such as '' E. coli'' and ''Salmonella'' with a common structural archit ...

found on

Gram-negative bacteria Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the Crystal violet, crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelo ...

, but members of this family may have many other functions. BPIFfamily-BPIFB2

Genes for the BPI/LBP/PLUNC superfamily are found in all vertebrate species, including distant

homologs Homologous chromosomes or homologs are a set of one maternal and one paternal chromosome that pair up with each other inside a cell during meiosis. Homologs have the same genes in the same loci, where they provide points along each chromosome th ...

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 chain-like biological molecule, such as a protein or nucleic acid, a structural motif is a common three-dimensional structure that appears in a variety of different, evolutionarily unrelated molecules. A structural motif does not have t ...

and are found clustered on a single chromosome, e.g.,

Chromosome 20 Chromosome 20 is one of the 23 pairs of chromosomes in humans. Chromosome 20 spans around 66 million base pairs (the building material of DNA) and represents between 2 and 2.5 percent of the total DNA in cells. Chromosome 20 was fully sequenced i ...

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 BPI fold containing family A, member 2 (BPIFA2), also known as Parotid Secretory Protein (PSP), is a protein that in humans is encoded by the ''BPIFA2'' gene. The ''BPIFA2'' gene sequence predicts multiple transcripts ( splice variants); 2 mRNA ...

'', ''

BPIFA3 BPI fold containing family A, member 3 (BPIFA3) is a protein that in humans is encoded by the ''BPIFA3'' gene. The gene is also known as ''SPLUNC3'' and ''C20orf71'' in humans and the orthologous gene in mice is ''1700058C13Rik''. There are multi ...

'', and 1 pseudogene ''

BPIFA4P BPI fold containing family A, member 4 (BPIFA4) is a non-human protein encoded by the ''Bpifa4'' gene in mammals such as monkey, cat, and cow but does not appear in rodents and humans. It is also known as Latherin in horse, encoded by the ''Lath/ ...

''; while BPIFB consists of 5 protein encoding genes ''

BPIFB1 BPI fold-containing family B member 1 (BPIFB1) is a protein that in humans is encoded by the ''BPIFB1'' gene. BPIFB1 is a secreted protein, expressed at very high levels in mucosa of the airways (respiratory and olfactory epithelium) and salivary ...

'', ''BPIFB2'', ''

BPIFB3 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 defined by the presenc ...

'', ''

BPIFB4 BPI fold containing family B, member 4 (BPIFB4) is a protein that in humans is encoded by the BPIFB4 gene. It was formerly known as "Long palate, lung and nasal epithelium carcinoma-associated protein 4" encoded by the ''LPLUNC4'' gene. The ''BPIF ...

'', ''

BPIFB6 BPI fold containing family B, member 6 (BPIFB6), also known as bactericidal/permeability-increasing protein-like 3 (BPIL3), is a protein that in humans is encoded by the ''BPIFB6'' gene, also known as ''BPIL3'' and ''LPLUNC6''. It is expressed at ...

'' and 2 pseudogenes ''

BPIFB5P BPI fold containing family B, member 5 is a non-human protein encoded by the ''Bpifb5'' gene, also known as ''Lplunc5.'' The BPIFB5 protein and ''Bpifb5'' gene have been characterized in mammals such as rodents (mouse, rat) and even-toed ungulate ...

'', ''

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 mo ...

''. What appears as pseudogenes in humans may appear as fully functional genes in other species. In humans, the ''BPIFB2'' gene was first identified as a ''BPIL3'' gene whose encoded protein was called LPLUNC2 (long-palate lung and nasal epithelium clone 2), but subsequently PLUNC proteins were classified as a subfamily of the BPI fold superfamily. In humans, the ''BPIFB2'' gene is found with other members of the BPI/LBP/PLUNC superfamily in a cluster on Chromosome 20.

Function

The BPIFB2 protein is involved in the innate immune response to bacterial exposure in the mucosa of the mouth, nasal cavities, and lungs, like other closely related BPIFB proteins. In particular, it is highly expressed in normal salivary glands and esophagus as well as in

hypertrophic Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It is distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number. Although hypertro ...

tonsils in humans. In chronic rhinosinusitis BPIFB2/LPLUNC2 levels are profoundly reduced which has been interpreted as a defect in the release of glandular innate defense molecules.

Superfamily

Function

References

External links

Further reading