DEFA4
Encyclopedia
Defensin, alpha 4 also known as neutrophil defensin 4 or HNP4, is a human defensin
peptide
that is encoded by the DEFA4 gene
. The human variant of the peptide is known as human alpha defensin 4 or human neutrophil peptide 4 (HNP4). HNP4 is expressed in the granules of the neutrophil where it defends the host against bacteria
and viruses.
family of cytotoxic microbicides involved in innate immunity. Members of the defensin family are distinguished by a conserved six-cysteine
motif. Several human alpha defensin genes including HNP4 are clustered on chromosome 8. DEFA4 differs from other defensin genes by an extra 83-base segment that is apparently the result of a recent duplication within the coding region. HNP4 inhibits corticotropin-stimulated corticosterone
production.
Defensin
Defensins are small cysteine-rich cationic proteins found in both vertebrates and invertebrates. They have also been reported in plants. They are, and function as, host defense peptides. They are active against bacteria, fungi and many enveloped and nonenveloped viruses. They consist of 18-45 amino...
peptide
Peptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...
that is encoded by the DEFA4 gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
. The human variant of the peptide is known as human alpha defensin 4 or human neutrophil peptide 4 (HNP4). HNP4 is expressed in the granules of the neutrophil where it defends the host against bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
and viruses.
Function
Defensins are a peptidePeptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...
family of cytotoxic microbicides involved in innate immunity. Members of the defensin family are distinguished by a conserved six-cysteine
Cysteine
Cysteine is an α-amino acid with the chemical formula HO2CCHCH2SH. It is a non-essential amino acid, which means that it is biosynthesized in humans. Its codons are UGU and UGC. The side chain on cysteine is thiol, which is polar and thus cysteine is usually classified as a hydrophilic amino acid...
motif. Several human alpha defensin genes including HNP4 are clustered on chromosome 8. DEFA4 differs from other defensin genes by an extra 83-base segment that is apparently the result of a recent duplication within the coding region. HNP4 inhibits corticotropin-stimulated corticosterone
Corticosterone
Corticosterone is a 21-carbon steroid hormone of the corticosteroid type produced in the cortex of the adrenal glands.-Roles:In many species, including amphibians, reptiles, rodents and birds, corticosterone is a main glucocorticoid, involved in regulation of fuel, immune reactions, and stress...
production.