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/Bpifa4'' gene but is somewhat divergent from the other species. Latherin/BPIFA4 is a secreted protein found in saliva and sweat. In humans, no functional protein is expressed, therefore ''BPIFB4P'' is referred to as a

pseudogene Pseudogenes are nonfunctional segments of DNA that resemble functional genes. Pseudogenes can be formed from both protein-coding genes and non-coding genes. In the case of protein-coding genes, most pseudogenes arise as superfluous copies of fun ...

. However, a non-functional protein does appear; it known as BASE protein, secreted by breast cancer cell lines and salivary gland tissue (see section below).

Superfamily

BPIFA3 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 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-BPIF-A4P

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'', '' BPIFA2'', '' BPIFA3'', and 1 pseudogene ''BPIFA4P''; while BPIFB consists of 5 protein encoding genes '' BPIFB1'', '' BPIFB2'', '' BPIFB3'', '' BPIFB4'', '' BPIFB6'' and 2 pseudogenes '' BPIFB5P'', '' BPIFB9P''. What appears as pseudogenes in humans may appear as fully functional genes in other species.

Function

Although ''BPIFA4P'' is identified as a pseudogene in humans, the RNA sequence for a

putative {{Short pages monitor