https://www.wikidoc.org/index.php?title=Antimicrobial_peptides&feed=atom&action=historyAntimicrobial peptides - Revision history2024-03-29T15:43:52ZRevision history for this page on the wikiMediaWiki 1.40.0https://www.wikidoc.org/index.php?title=Antimicrobial_peptides&diff=668766&oldid=prevWikiBot: Bot: Automated text replacement (-{{SIB}} + & -{{EH}} + & -{{EJ}} + & -{{Editor Help}} + & -{{Editor Join}} +)2012-08-08T22:20:12Z<p>Bot: Automated text replacement (-{{SIB}} + & -{{EH}} + & -{{EJ}} + & -{{Editor Help}} + & -{{Editor Join}} +)</p>
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==Overview==<br />
'''Antimicrobial peptides''' (also called host defence peptides) are an evolutionarily conserved component of the innate immune response and are found among all classes of life. <br />
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These peptides are potent, broad spectrum [[antibiotic]]s which demonstrate potential as novel therapeutic agents. Antimicrobial peptides have been demonstrated to kill [[Gram negative]] and [[Gram positive]] bacteria (including strains that are resistant to conventional antibiotics), [[Mycobacterium|mycobacteria]] (including ''[[Mycobacterium tuberculosis]]''), enveloped viruses, fungi and even transformed or cancerous cells. Unlike the majority of conventional antibiotics it appears as though antimicrobial peptides may also have the ability to enhance immunity by functioning as [[immunomodulator]]s. <br />
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==Structure==<br />
Antimicrobial peptides are short [[protein]]s, generally between 12 and 50 [[amino acid]]s long (although larger proteins with similar properties such as [[lysozyme]] are often classified as antimicrobial peptides). These peptides include two or more positively charged residues provided by [[arginine]], [[lysine]] or, in acidic environments, [[histidine]], and a large proportion (generally >50%) of hydrophobic residues.{{ref|papagiannietal}}{{ref|sitarametal}} The secondary structures of these molecules follow 4 themes, including i) [[Alpha helix|α-helical]], ii) [[Beta sheet|β-stranded]] due to the presence of 2 or more [[disulphide bond]]s, iii) β-hairpin or loop due to the presence of a single disulphide bond and/or cyclization of the peptide chain, and iv) extended. Many of these peptides are unstructured in free solution, and fold into their final configuration upon partitioning into biological membranes. The ability to associate with membranes is a definitive feature of antimicrobial peptides {{ref|hancocketal}} although membrane permeabilisation is not necessary. These peptides have a variety of antimicrobial activities ranging from membrane permeabilization to action on a range of cytoplasmic targets.<br />
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==Antimicrobial Activities==<br />
The modes of action by which antimicrobial peptides kill bacteria is varied and includes disrupting membranes, interfering with metabolism, and targeting cytoplasmic components. In many cases the exact mechanism of killing is not known. In contrast to many conventional antibiotics these peptides appear to be [[bacteriocidal]] (bacteria killer) instead of [[bacteriostatic]] (bacteria growth inhibitor). In general the antimicrobial activity of these peptides is determined by measuring the minimal inhibitory concentration (MIC), which is the lowest concentration of drug that reduces growth by more than 50%.{{ref|nclssamsterdam}}<br />
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==Immunomodulatory Activities==<br />
In addition to killing bacteria directly they have been demonstrated to have a number of [[Immunomodulator|immunomodulatory]] functions that may be involved in the clearance of infection, including the ability to alter host gene expression, act as chemokines and/or induce [[chemokine]] production, inhibiting [[lipopolysaccharide]] induced pro-inflammatory [[cytokine]] production, promoting wound healing, and modulating the responses of [[dendritic cell]]s and cells of the adaptive immune response. Animal models indicate that host defence peptides are crucial for both prevention and clearance of infection. It appears as though many peptides initially isolated as and termed “antimicrobial peptides” have been shown to have more significant alternative functions in vivo (e.g. hepcidin {{ref|hunteretal}}). <br />
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==Therapeutic Potential==<br />
These peptides are excellent candidates for development as novel therapeutic agents and complements to conventional antibiotic therapy because in contrast to conventional antibiotics they do not appear to induce antibiotic resistance while they generally have a broad range of activity, are bacteriocidal as opposed to bacteriostatic and require a short contact time to induce killing. A number of naturally occurring peptides and their derivatives have been developed as novel anti-infective therapies for conditions as diverse as oral mucositis, lung infections associated with [[cystic fibrosis]] (CF) and topical skin infections.<br />
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==Notes and references==<br />
# {{note|papagiannietal}} Papagianni, M. 2003. Ribosomally synthesized peptides with antimicrobial properties: biosynthesis, structure, function, and applications. Biotechnol Adv 21:465.<br />
# {{note|sitarametal}} Sitaram, N., and R. Nagaraj. 2002. Host-defense antimicrobial peptides: importance of structure for activity. Curr Pharm Des 8:727.<br />
# {{note|hancocketal}} Hancock, R. E. W., and A. Rozek. 2002. Role of membranes in the activities of antimicrobial cationic peptides. FEMS Microbiol Lett 206:143.<br />
# {{note|nclssamsterdam}} National Committee of Laboratory Safety and Standards (NCLSS) as published in Amsterdam, D. 1996. Susceptibility testing of Antimicrobials in liquid media. In "Antibiotics in Laboratory Medicine", Lorian, V., ed. Fourth Edition, pp.52-111. Williams and Wilkins, Baltimore<br />
# {{note|hunteretal}} Hunter, H. N., D. B. Fulton, T. Ganz, and H. J. Vogel. 2002. The solution structure of human hepcidin, a peptide hormone with antimicrobial activity that is involved in iron uptake and hereditary hemochromatosis. J Biol Chem 277:37597.<br />
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== External links ==<br />
*[http://www.scq.ubc.ca/?p=405 A good basic overview of cationic peptides] at scq.ubc.ca<br />
*[http://www.ejbiotechnology.info/content/vol6/issue3/full/1/index.html Review with helpful links] at ejbiotechnology.info<br />
*[http://aps.unmc.edu/AP/main.php Antimicrobial Peptide Database] at unmc.edu<br />
* {{UMichOPM|classes|type|3}} - Calculated spatial positions of peptides in the lipid bilayer<br />
* {{MeshName|Antimicrobial+Cationic+Peptides}}<br />
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==See also==<br />
[[Cathelicidin]]<br />
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[[Category:Immunology]]<br />
[[Category:Immune system]]<br />
[[Category:Peripheral membrane proteins]]<br />
[[Category:Antimicrobial peptides]]<br />
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{{WS}}</div>Brian Blank