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Defensins: endogenous antibiotic peptides from human leukocytes
1Department of Medicine, University of California, Los Angeles 90024.
Ciba Foundation Symposium
|January 1, 1992
Summary
Defensins are key antimicrobial peptides in mammals, crucial for innate immunity. These small proteins defend against a wide range of pathogens by forming channels in microbial membranes.
Area of Science:
- Biochemistry
- Immunology
- Molecular Biology
Background:
- Mammals, amphibians, insects, and plants possess endogenous antimicrobial peptides for pathogen defense.
- Defensins are small (29-35 amino acid) mammalian peptides with six invariant cysteines forming three disulfide bonds.
- They derive from ~95 amino acid precursors, synthesized by various cells, notably bone marrow neutrophil precursors.
Purpose of the Study:
- To detail the structure, synthesis, and function of mammalian defensins.
- To highlight the role of defensins in innate immunity against microbial pathogens.
Main Methods:
- Analysis of defensin precursor processing and cellular localization.
- Characterization of defensin structure, including folding and amphipathic properties.
- Assessment of defensin antimicrobial spectrum and mechanism of action.
Main Results:
- Defensins comprise 5-7% of human neutrophil protein, concentrated in granules and vacuoles.
- Human neutrophils produce approximately 10 mg/kg body weight of defensins daily.
- Defensins exhibit broad-spectrum activity against bacteria, fungi, mycobacteria, spirochetes, and viruses.
- Antimicrobial action involves membrane insertion and formation of voltage-sensitive channels.
Conclusions:
- Defensins are abundant, structurally complex peptides with potent, broad-spectrum antimicrobial activity.
- Their mechanism involves membrane disruption, contributing significantly to innate resistance against infections.