Biology:DEFA1

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Short description: Protein-coding gene in the species Homo sapiens


A representation of the 3D structure of the protein myoglobin showing turquoise α-helices.
Generic protein structure example

Defensin, alpha 1 also known as human alpha defensin 1, human neutrophil peptide 1 (HNP-1) or neutrophil defensin 1 is a human protein that is encoded by the DEFA1 gene.[1][2][3] Human alpha defensin 1 belongs to the alpha defensin family of antimicrobial peptides.

Function

Defensins are a family of microbicidal and cytotoxic peptides thought to be involved in host defense. They are abundant in the granules of neutrophils and also found in the epithelia of mucosal surfaces such as those of the intestine, respiratory tract, urinary tract, and vagina. Members of the defensin family are highly similar in protein sequence and distinguished by a conserved cysteine motif. Several alpha defensin genes are clustered on chromosome 8. The protein encoded by this gene, defensin, alpha 1, is found in the microbicidal granules of neutrophils and likely plays a role in phagocyte-mediated host defense. It differs from the defensins, alpha 2 and alpha 3 by only one amino acid.[3]

Biosynthesis

HNPs are generated as 94 amino acids preproHNPs, which are co-translationally cleaved to 75 amino acids pro-peptides with a N-terminal prosegment having a negative charge that neutralizes the highly positively charged C terminal peptide. Processing of proHNPs occurs mainly in late promyelocytes, where the 75 amino acids proHNPs are cleaved to a 56 amino acids intermediate form and onward to 29-30 amino acids mature peptides designated HNPs.[4][5] Cationic 29-30 amino acids HNPs associate with the negatively charged proteoglycan serglycin and translocate to azurophil granules.[6] At later stages of granulocytic differentiation in which HNP expression peaks (i.e. myelocytes and metamyelocytes), proHNPs are not cleaved, rendering the peptides overall neutral. This prevents binding to serglycin and most proHNP is accordingly secreted into the bone marrow plasma although some is retained in specific granules.[7]

References

  1. ↑ "Fragile X mental retardation protein: nucleocytoplasmic shuttling and association with somatodendritic ribosomes". J Neurosci 17 (5): 1539–47. Mar 1997. doi:10.1523/JNEUROSCI.17-05-01539.1997. PMID 9030614. 
  2. ↑ "Copy number polymorphism and expression level variation of the human alpha-defensin genes DEFA1 and DEFA3". Hum Mol Genet 14 (14): 2045–52. Jul 2005. doi:10.1093/hmg/ddi209. PMID 15944200. 
  3. ↑ 3.0 3.1 "Entrez Gene: DEFA1 defensin, alpha 1". https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=1667. 
  4. ↑ "Posttranslational processing of defensins in immature human myeloid cells.". Blood 79 (6): 1538–44. Mar 15, 1992. doi:10.1182/blood.V79.6.1538.1538. PMID 1339298. 
  5. ↑ "Timing, targeting and sorting of azurophil granule proteins in human myeloid cells.". Leukemia 12 (11): 1789–95. Nov 1998. doi:10.1038/sj.leu.2401202. PMID 9823955. 
  6. ↑ "Serglycin participates in retention of α-defensin in granules during myelopoiesis.". Blood 118 (16): 4440–8. Oct 20, 2011. doi:10.1182/blood-2011-06-362947. PMID 21849484. 
  7. ↑ "Prodefensins are matrix proteins of specific granules in human neutrophils.". Journal of Leukocyte Biology 78 (3): 785–93. Sep 2005. doi:10.1189/jlb.1104688. PMID 15944211. 

Further reading




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