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STRUCTURAL, FUNCTIONAL AND EVOLUTIONARY STUDIES OF ANTIMICROBIAL PEPTIDES

Pasupuleti, Mukesh LU (2009) In Lund University, Faculty of Medicine Doctoral Dissertation Series 2009:85.
Abstract
Antimicrobial peptides represent a heterogeneous group that displays multiple modes of action such as bacteriostatic, microbicidal and cytolytic properties that are sequence and concentration dependent. Life threatening infectious disease is now a worldwide crisis and treating them effectively is becoming difficult day by day, due to the emergence of antibiotic resistant strains at alarming rates. Hence, there is an urgent need for new class of antibiotics and, antimicrobial peptides (AMPs) are an ideal candidate for this job. AMPs are gene encoded short (<100 amino acids), amphipathic molecules with hydrophobic and cationic amino acids arranged spatially which exhibit broad-spectrum antimicrobial activity. AMPs form an ancient... (More)
Antimicrobial peptides represent a heterogeneous group that displays multiple modes of action such as bacteriostatic, microbicidal and cytolytic properties that are sequence and concentration dependent. Life threatening infectious disease is now a worldwide crisis and treating them effectively is becoming difficult day by day, due to the emergence of antibiotic resistant strains at alarming rates. Hence, there is an urgent need for new class of antibiotics and, antimicrobial peptides (AMPs) are an ideal candidate for this job. AMPs are gene encoded short (<100 amino acids), amphipathic molecules with hydrophobic and cationic amino acids arranged spatially which exhibit broad-spectrum antimicrobial activity. AMPs form an ancient non-specific type of innate immunity found universally in all living organisms and used as the principal first line of defense against the invading pathogen. AMPs have been in the process of evolution, as have the microbes, for hundreds of years. Despite the long history of co-evolution, AMPs have not lost their ability to kill the microbes totally nor have the microbes learnt to avoid the lethal punch of AMPs. Based upon accumulating positive data, we are encouraged to believe that antimicrobial peptides have a great potential to be the next breakthrough and first novel, truly biological in nature, class of antibiotics.

The purpose of this study was twofold; primarily to elucidate the factors involved in governing the peptide activity and toxicity against membranes, and secondly to design a simple approach where we can boost and spread the spectrum of antimicrobial activity against pathogens such as S. aureus and P. aeruginosa for a peptide that is otherwise non-lethal to the bacteria. Results presented in this thesis show that antimicrobial domains of the anaphylatoxin C3a are structurally and evolutionary conserved. Moreover antimicrobial activity is not governed by a single factor, but instead by a combination of net charge, amphipathicity and helicity. By utilizing a low number of amino acid substitutions at strategic positions in an antimicrobial peptide derived from C3a, CNY20, we were able to develop peptides, which exert a significant activity on both S. aureus and C. albicans in contrast to the parent peptide. Although, antimicrobial activity is not governed by single parameter, the activity can still be boosted by end-tagging of a peptide with hydrophobic oligopeptide stretches. This modification promotes peptide binding to bacteria and subsequent cell wall rupture, but does not increase the toxicity or the protease susceptibility of the peptide. It is noteworthy that end tagging of ultra short peptides spanning 5-7 amino acids with hydrophobic amino acids enhances bactericidal activity, while preserving low toxicity and protease resistance. (Less)
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author
supervisor
opponent
  • Prof. Andersson, Mats, Vetenskaplig sekreterare, Karolinska Institutet , Forsknings- och Forskarutbildningsavdelningen, Nobels väg 5, S-171 77 Stockholm, Sweden
organization
publishing date
type
Thesis
publication status
published
subject
keywords
amphipathicity and end-tagging protease susceptibility, anaphylatoxin C3a, P. aeruginosa, S. aureus, innate immunity, amphipathic molecules, Antimicrobial peptides, infectious disease, bacteriostatic, microbicidal and cytolytic properties
in
Lund University, Faculty of Medicine Doctoral Dissertation Series
volume
2009:85
pages
198 pages
publisher
Department of Clinical Sciences, Lund University
defense location
GK-salen, Biomedicinskt Centrum, Sölvegatan 19.
defense date
2009-09-30 09:15
ISSN
1652-8220
ISBN
978-91-86253-73-8
language
English
LU publication?
yes
id
f83aeb26-cd64-4762-bc76-14d279a09808 (old id 1470860)
date added to LUP
2009-09-03 08:55:12
date last changed
2016-09-19 08:44:50
@phdthesis{f83aeb26-cd64-4762-bc76-14d279a09808,
  abstract     = {Antimicrobial peptides represent a heterogeneous group that displays multiple modes of action such as bacteriostatic, microbicidal and cytolytic properties that are sequence and concentration dependent. Life threatening infectious disease is now a worldwide crisis and treating them effectively is becoming difficult day by day, due to the emergence of antibiotic resistant strains at alarming rates. Hence, there is an urgent need for new class of antibiotics and, antimicrobial peptides (AMPs) are an ideal candidate for this job. AMPs are gene encoded short (&lt;100 amino acids), amphipathic molecules with hydrophobic and cationic amino acids arranged spatially which exhibit broad-spectrum antimicrobial activity. AMPs form an ancient non-specific type of innate immunity found universally in all living organisms and used as the principal first line of defense against the invading pathogen. AMPs have been in the process of evolution, as have the microbes, for hundreds of years. Despite the long history of co-evolution, AMPs have not lost their ability to kill the microbes totally nor have the microbes learnt to avoid the lethal punch of AMPs. Based upon accumulating positive data, we are encouraged to believe that antimicrobial peptides have a great potential to be the next breakthrough and first novel, truly biological in nature, class of antibiotics. <br/><br>
The purpose of this study was twofold; primarily to elucidate the factors involved in governing the peptide activity and toxicity against membranes, and secondly to design a simple approach where we can boost and spread the spectrum of antimicrobial activity against pathogens such as S. aureus and P. aeruginosa for a peptide that is otherwise non-lethal to the bacteria. Results presented in this thesis show that antimicrobial domains of the anaphylatoxin C3a are structurally and evolutionary conserved. Moreover antimicrobial activity is not governed by a single factor, but instead by a combination of net charge, amphipathicity and helicity. By utilizing a low number of amino acid substitutions at strategic positions in an antimicrobial peptide derived from C3a, CNY20, we were able to develop peptides, which exert a significant activity on both S. aureus and C. albicans in contrast to the parent peptide. Although, antimicrobial activity is not governed by single parameter, the activity can still be boosted by end-tagging of a peptide with hydrophobic oligopeptide stretches. This modification promotes peptide binding to bacteria and subsequent cell wall rupture, but does not increase the toxicity or the protease susceptibility of the peptide. It is noteworthy that end tagging of ultra short peptides spanning 5-7 amino acids with hydrophobic amino acids enhances bactericidal activity, while preserving low toxicity and protease resistance.},
  author       = {Pasupuleti, Mukesh},
  isbn         = {978-91-86253-73-8},
  issn         = {1652-8220},
  keyword      = {amphipathicity and end-tagging protease susceptibility,anaphylatoxin C3a,P. aeruginosa,S. aureus,innate immunity,amphipathic molecules,Antimicrobial peptides,infectious disease,bacteriostatic,microbicidal and cytolytic properties},
  language     = {eng},
  pages        = {198},
  publisher    = {Department of Clinical Sciences, Lund University},
  school       = {Lund University},
  series       = {Lund University, Faculty of Medicine Doctoral Dissertation Series},
  title        = {STRUCTURAL, FUNCTIONAL AND EVOLUTIONARY STUDIES OF ANTIMICROBIAL PEPTIDES},
  volume       = {2009:85},
  year         = {2009},
}