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 ungulates (pig, cow) but are apparently lacking in primates and other vertebrates such as birds, reptiles, and amphibians. The protein in rodents is expressed at moderately high levels in

mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

of the airways (respiratory and olfactory

epithelium Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...

) and at moderate levels in salivary glands, esophagus, and gonads (

ovary The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. ...

, testis); in even-toed ungulates expression is high in testis, moderate in brain and striated muscle, and low in kidney. In humans no protein is expressed and it is present only as a

pseudogene Pseudogenes are nonfunctional segments of DNA that resemble functional genes. Most arise as superfluous copies of functional genes, either directly by DNA duplication or indirectly by Reverse transcriptase, reverse transcription of an mRNA trans ...

''BPIFB5P''. The pseudogene was named based on its functional ortholog found in the other species.

Superfamily

BPIFB5 is a member of the 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-BPIFB5P

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 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'', and 1 pseudogene ''

BPIFA4P BPI fold containing family A, member 4 (BPIFA4) is a non-human protein encoded by the ''Bpifa4'' gene in monkey and cow. It is also known as Latherin in horse, encoded by the ''Lath/Bpifa4'' gene but somewhat divergent from the other species. Lat ...

''; 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 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 prese ...

'', '' BPIFB4'', ''

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 ...

'' 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. The human ''BPIFB5P'' pseudogene is found clustered with other members of the BPIF gene family conforming to the pattern observed in mammals, but this is not the case for other vertebrate species. In a systematic analysis of the chicken genome, the '' Lplunc1(Bpifb1) / Lplunc5(Bpifb5)'' branch of the gene family was determined to be absent, therefore BPIFB1 and BPIFB5 proteins likely arose only after the speciation of mammals.

References

External links

* {{UCSC gene info, BPIFB5P Pseudogenes Genes on human chromosome 20