Antimicrobial peptides derived from the human bactericidal/permeability-increasing protein (BPI) : structural determinants and mechanism of action
Antimicrobial peptides derived from the human bactericidal/permeability-increasing protein (BPI) : structural determinants and mechanism of action
Bactericidal/Permeability-Increasing protein (BPI) is a 456 residue cationic protein from human neutrophils that binds with high affinity ot lipopolysaccharide (LPS) and specifically kills Gram-negative bacteria. Both of these properties of BPI are found in a proteolytic fragment corresponding to the amino-terminal portion of the protein, however, the precise mechanism of bactericidal activity of BPI is still unknown. Studies indicate that peptides containing residues 86-104 of BPI are sufficient for antibacterial activity and that these peptides are also able to kill Gram-positive bacteria.
Peptides were synthesised which contained amino acid residues 90-99 and flanking regions of BPI. Of these, peptide P2 (SKISGKWKAQKRFLKMSGNFGC) was used to study the physiological effects of peptide interaction with Escherichia coli ML35. The effect of P2 on macromolecular synthesis, colony-forming ability, cytoplasmic membrane (CM) and other membrane (OM) permeabilisation were studied concurrently so that they could be placed in chronological order. The growth-phase of E. coli was found to be important for the chronology of events: in exponential-phase E. coli ML35 (108 cells/ml) treated with P2 (50 μg/ml), the OM became permeabilised and O2-consumption stopped within minutes of peptide addition. Within 15 minutes, the CM was permeabilised and macromolecular synthesis stopped. With stationary-phase bacteria, the OM was permeabilised and O2-consumption stopped within 5 minutes of peptide addition; but, in contrast to exponential-phase cells, permeabilisation of the CM occurred much later, approximately 30 minutes following peptide addition. Cessation of O2-consumption was one of the earliest measurable effects of P2 on E. coli. Studies using different carbon sources showed that the presence of formate or certain other carbon sources, prevented this effect and also rescued E. coli form the antibacterial effects of P2. Further work indicated that formate dehydrogenase O or N were involved in the formate-dependant rescue, although the full reason for this phenomenon is not yet fully understood.
University of Southampton
1997
Barker, Helen Claire
(1997)
Antimicrobial peptides derived from the human bactericidal/permeability-increasing protein (BPI) : structural determinants and mechanism of action.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Bactericidal/Permeability-Increasing protein (BPI) is a 456 residue cationic protein from human neutrophils that binds with high affinity ot lipopolysaccharide (LPS) and specifically kills Gram-negative bacteria. Both of these properties of BPI are found in a proteolytic fragment corresponding to the amino-terminal portion of the protein, however, the precise mechanism of bactericidal activity of BPI is still unknown. Studies indicate that peptides containing residues 86-104 of BPI are sufficient for antibacterial activity and that these peptides are also able to kill Gram-positive bacteria.
Peptides were synthesised which contained amino acid residues 90-99 and flanking regions of BPI. Of these, peptide P2 (SKISGKWKAQKRFLKMSGNFGC) was used to study the physiological effects of peptide interaction with Escherichia coli ML35. The effect of P2 on macromolecular synthesis, colony-forming ability, cytoplasmic membrane (CM) and other membrane (OM) permeabilisation were studied concurrently so that they could be placed in chronological order. The growth-phase of E. coli was found to be important for the chronology of events: in exponential-phase E. coli ML35 (108 cells/ml) treated with P2 (50 μg/ml), the OM became permeabilised and O2-consumption stopped within minutes of peptide addition. Within 15 minutes, the CM was permeabilised and macromolecular synthesis stopped. With stationary-phase bacteria, the OM was permeabilised and O2-consumption stopped within 5 minutes of peptide addition; but, in contrast to exponential-phase cells, permeabilisation of the CM occurred much later, approximately 30 minutes following peptide addition. Cessation of O2-consumption was one of the earliest measurable effects of P2 on E. coli. Studies using different carbon sources showed that the presence of formate or certain other carbon sources, prevented this effect and also rescued E. coli form the antibacterial effects of P2. Further work indicated that formate dehydrogenase O or N were involved in the formate-dependant rescue, although the full reason for this phenomenon is not yet fully understood.
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Published date: 1997
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Local EPrints ID: 463150
URI: http://eprints.soton.ac.uk/id/eprint/463150
PURE UUID: c1823a98-5cb5-4cd5-a017-dfbe1ca6e01b
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Date deposited: 04 Jul 2022 20:46
Last modified: 04 Jul 2022 20:46
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Author:
Helen Claire Barker
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