BD 4 Human
Description
Definition and Classification
Beta Defensin-4 Human (BD-4), also known as human beta-defensin-4 (hBD-4), is a cationic antimicrobial peptide belonging to the beta-defensin family, a critical component of the innate immune system . It is a 50-amino-acid peptide with a molecular weight of ~6 kDa, characterized by a conserved six-cysteine motif that forms three intramolecular disulfide bonds, essential for its structural stability and function .
| Property | Value | Source |
|---|---|---|
| Amino acid length | 50 amino acids | |
| Molecular weight | ~6 kDa | |
| Disulfide bonds | Three (Cys-Cys) | |
| Charge (pH 7) | Cationic |
BD-4 is expressed at epithelial surfaces and by select leukocytes, functioning as both a direct antimicrobial agent and an immunomodulator .
Antimicrobial Activity
BD-4 exhibits broad-spectrum activity against Gram-positive and Gram-negative bacteria, including multidrug-resistant (MDR) strains. Key findings include:
Antibacterial Spectrum
BD-4 retains ~80% activity under high salt concentrations (150 mM), a critical advantage for clinical applications in salty environments like wounds .
Mechanism of Action
BD-4’s antimicrobial effects are mediated through two primary pathways:
Membrane Disruption
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Electrostatic Interaction: The peptide’s positive charge enables binding to negatively charged microbial membranes (e.g., lipopolysaccharides in Gram-negative bacteria) .
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Pore Formation: Aggregation of BD-4 molecules creates transmembrane pores, leading to cytoplasmic leakage and microbial death .
Immunomodulatory Effects
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Chemotaxis: Attracts immune cells (e.g., dendritic cells, T-cells) to infection sites .
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Anti-inflammatory Modulation: Reduces pro-inflammatory cytokine release (e.g., IL-6, TNF-α) in some contexts .
Production and Recombinant Technology
BD-4 is typically produced via recombinant bacterial systems (e.g., E. coli) due to its small size and lack of glycosylation. Challenges include low yields and oxidative folding inefficiencies .
| Production Method | Advantages | Limitations |
|---|---|---|
| E. coli expression | High scalability, low cost | Disulfide bond misfolding |
| Yeast/mammalian systems | Native folding | Higher production costs |
| Synthetic peptide | Precise sequence control | Limited to short peptides |
Purification involves chromatography (e.g., RP-HPLC, SDS-PAGE), yielding >95% purity .
Therapeutic Potential
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Wound Healing: BD-4 promotes angiogenesis and tissue repair by stimulating fibroblast migration and endothelial cell proliferation .
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Targeted Therapy: Chimeric derivatives (e.g., H4, combining hBD-3/hBD-4) enhance salt tolerance and broaden antimicrobial coverage .
Challenges
Product Specs
Currently, four human Beta-defensins have been discovered: BD-1, BD-2, BD-3, and BD-4.
These Beta-defensins are found on certain white blood cells and the surfaces of epithelial tissues.
Beyond their direct antimicrobial properties, they act as signaling molecules, attracting immature dendritic cells and memory T cells. Beta-defensin proteins originate as the tail end of larger precursor proteins. They are cleaved from these precursors through enzymatic reactions, shedding a signal sequence and, in the case of BD-1 (36 amino acids), a propeptide segment. Characteristically, Beta-defensins contain a specific arrangement of six cysteine amino acids, forming three disulfide bonds within the molecule. These peptides are relatively small, with molecular weights ranging from 3-5 kDa and composed of 33-47 amino acid residues.
The purification of BD-4 is achieved through specialized chromatographic techniques.
Repeated cycles of freezing and thawing should be avoided.
(a) Reverse-Phase High-Performance Liquid Chromatography (RP-HPLC) analysis.
(b) Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) analysis.
Product Science Overview
Beta Defensin-4 (BD-4), also known as human beta-defensin 4 (hBD-4), is a member of the defensin family of antimicrobial peptides. These peptides play a crucial role in the innate immune system by providing a first line of defense against a wide range of pathogens, including bacteria, fungi, and viruses. Defensins are characterized by their cationic nature and the presence of six cysteine residues that form three intramolecular disulfide bonds, which are essential for their stability and function.
Beta Defensin-4 is a small peptide consisting of 50 amino acids and has a molecular mass of approximately 6 kilodaltons . The peptide is produced as a single, non-glycosylated polypeptide chain. The amino acid sequence of Beta Defensin-4 is as follows:
EFELDRICGY GTARCRKKCR SQEYRIGRCP NTYACCLRKW DESLLNRTKP
The structure of Beta Defensin-4 includes a six-cysteine motif that forms three intramolecular disulfide bonds, which are crucial for its antimicrobial activity and stability .
Human recombinant Beta Defensin-4 is typically produced using Escherichia coli (E. coli) expression systems. The recombinant peptide is purified using proprietary chromatographic techniques to achieve a purity greater than 98%, as determined by reverse-phase high-performance liquid chromatography (RP-HPLC) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) .
Beta Defensin-4 exhibits a broad spectrum of antimicrobial activity. It is effective against a variety of Gram-positive and Gram-negative bacteria, fungi, and viruses. The peptide exerts its antimicrobial effects by disrupting the microbial cell membrane, leading to cell lysis and death .
In addition to its direct antimicrobial activity, Beta Defensin-4 also has immunomodulatory properties. It acts as a chemoattractant for immature dendritic cells and memory T cells, thereby enhancing the immune response . The biological activity of Beta Defensin-4 is determined by its ability to chemoattract human monocytes at concentrations ranging from 0.1 to 50 nanograms per milliliter .
Lyophilized (freeze-dried) Beta Defensin-4 is stable at room temperature for up to three weeks. For long-term storage, it should be kept desiccated below -18°C. Upon reconstitution, the peptide should be stored at 4°C for short-term use (2-7 days) and below -18°C for long-term use. It is important to avoid repeated freeze-thaw cycles to maintain the peptide’s stability and activity .
Beta Defensin-4 holds promise for various therapeutic applications due to its potent antimicrobial and immunomodulatory properties. Potential applications include:
- Treatment of Infections: Beta Defensin-4 could be used as a therapeutic agent to treat bacterial, fungal, and viral infections, particularly those that are resistant to conventional antibiotics.
- Wound Healing: The peptide’s ability to attract immune cells to the site of infection or injury suggests potential use in promoting wound healing and tissue repair.
- Cancer Therapy: Emerging research indicates that defensins, including Beta Defensin-4, may have anticancer properties, making them potential candidates for cancer therapy.
