Beta-defensin 2

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Protein DEFB4 PDB 1e4q.png
Available structures
PDB Human UniProt search: PDBe RCSB
Aliases DEFB4A, BD-2, DEFB-2, DEFB102, DEFB2, DEFB4, HBD-2, SAP1, Beta-defensin 2, defensin beta 4A
External IDs HomoloGene: 122147 GeneCards: DEFB4A
Gene location (Human)
Chromosome 8 (human)
Chr. Chromosome 8 (human)[1]
Chromosome 8 (human)
Genomic location for DEFB4A
Genomic location for DEFB4A
Band 8p23.1 Start 7,894,629 bp[1]
End 7,896,711 bp[1]
Species Human Mouse
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC) Chr 8: 7.89 – 7.9 Mb n/a
PubMed search [2] n/a
View/Edit Human

Beta-defensin 2 (BD-2) also known as skin-antimicrobial peptide 1 (SAP1) is a peptide that in humans is encoded by the DEFB4 (defensin, beta 4) gene.[3]

Human beta-defensin-2 (hBD-2) is a cysteine-rich cationic low molecular weight antimicrobial peptide recently discovered in lesional skin.


hBD-2 is a protein whose primary structure is made by 64 aminoacids. At concentrations ≤2.4 mM, hBD-2 is monomeric.[4] The structure is amphiphilic with a nonuniform surface distribution of positive charge and contains several key structural elements, including a triple-stranded, antiparallel beta sheet with strands 2 and 3 in a beta hairpin conformation. The determination of other structural elements depends on the technique used. When X-ray crystallography is used an alpha helix can be observed at the C-terminal end of the protein (PDB code: 1fd3​). When using NMR this alpha-helix does not appear (PDB code: 1e4q​).


Defensins form a family of microbicidal and cytotoxic peptides made by neutrophils. Members of the defensin family are highly similar in protein sequence. Beta-defensin 2 is an antibiotic peptide which is locally regulated by inflammation.[5]

Human beta-defensin 2 is produced by a number of epithelial cells and exhibits potent antimicrobial activity against Gram-negative bacteria and Candida, but not Gram-positive S. aureus. It has been speculated that beta-defensin 2 may contribute to the infrequency of Gram-negative infections on skin and lung tissue.[6]

hBD-2 represents the first human defensin that is produced following stimulation of epithelial cells by contact with microorganisms such as P. aeruginosa or cytokines such as TNF-alpha and IL-1 beta. The HBD-2 gene and protein are locally expressed in keratinocytes associated with inflammatory skin lesions. It is intriguing to speculate that HBD-2 is a dynamic component of the local epithelial defense system of the skin and respiratory tract having a role to protect surfaces from infection, and providing a possible reason why skin and lung infections with Gram-negative bacteria are rather rare.[6]

Although this protein doesn’t have any antibacterial activity against Gram-positive bacteria, there is a study showing that there is a synergy between hBD-2 and other proteins.[7] One example of this synergistic effect is with epiP, a protein segregated by some strains of S. epidermidis. hBD2, holding hands with epiP, is capable of killing S. aureus, a Gram-positive bacteria responsible of human diseases.


  1. ^ a b c ENSG00000285181 GRCh38: Ensembl release 89: ENSG00000171711, ENSG00000285181 - Ensembl, May 2017
  2. ^ "Human PubMed Reference:". 
  3. ^ Harder J, Bartels J, Christophers E, Schroder JM (Jul 1997). "A peptide antibiotic from human skin". Nature. 387 (6636): 861. doi:10.1038/43088. PMID 9202117. 
  4. ^ Sawai MV, Jia HP, Liu L, Aseyev V, Wiencek JM, McCray PB Jr, Ganz T, Kearney WR, Tack BF (2001). "The NMR structure of human beta-defensin-2 reveals a novel alpha-helical segment". Biochemistry. 40 (13): 3810–3816. doi:10.1021/bi002519d. PMID 11300761. 
  5. ^ "Entrez Gene: DEFB4 defensin, beta 4". 
  6. ^ a b Schröder JM, Harder J (June 1999). "Human beta-defensin-2". Int. J. Biochem. Cell Biol. 31 (6): 645–51. doi:10.1016/S1357-2725(99)00013-8. PMID 10404637. 
  7. ^ Tadayuki Iwase; Yoshio Uehara; Hitomi Shinji; Akiko Tajima; Hiromi Seo; Koji Takada; Toshihiko Agata; Yoshimitsu Mizunoe (2010). ""Staphylococcus epidermidis Esp inhibits Staphylococcus aureus biofilm formation and nasal colonization"". Nature. 465 (7296): 346–349. doi:10.1038/nature09074. PMID 20485435. 

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