Oxygen-Independent Bactericidal Systems: Mechanisms and Disorders

Lehrer, R. I.; Ganz, Tomas; Selsted, Michael E.

doi:10.1016/s0889-8588(18)30635-x

Cited by 36 publications

(20 citation statements)

References 47 publications

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“…That normal human PMN kill ingested gram-negative bacteria with considerable efficacy under anaerobic conditions suggests that these cells possess potent 02-independent bactericidal mechanisms (9,27,28). In addition to defensins, the azurophil granules of human PMN contain two other wellcharacterized components, bactericidal/permeability-increasing protein (B/PI) and cathepsin G, able to kill E. coli in vitro.…”

Section: Discussionmentioning

confidence: 99%

Interaction of human defensins with Escherichia coli. Mechanism of bactericidal activity.

Lehrer¹,

Barton²,

Daher³

et al. 1989

J. Clin. Invest.

672

516

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Defensins are smalL cysteine-rich antimicrobial peptides that are abundant in human, rabbit, and guinea pig neutrophils (PMN). Three defensins (human neutrophil peptide defensin constitute between 30 and 50% of the total protein in azurophil granules of human PMN. We examined the mechanism of HNP-mediated bactericidal activity against Escherichia coli ML-35 (i-, y-, z+) and its pBR322-transformed derivative, E. coli ML-35p. Under conditions that supported bactericidal activity, HNP-1 sequentially permeabilized the outer membrane (OM) and inner membrane (IM) of E. coli. Coincident with these events, bacterial synthesis of DNA, RNA, and protein ceased and the colony count fell. Although these events were closely coupled under standard assay conditions, OM permeabilization was partially dissociated from IM permeabilization when experiments were performed with E. coli that had been plasmolyzed by mannitol. Under such conditions, the rate and extent of bacterial death more closely paralleled loss of IM integrity than OM permeabilization. Electron microscopy of E. coli that had been killed by defensins revealed the presence of striking electron-dense deposits in the periplasmic space and affixed to the OM.Overall, these studies show that HNP-mediated bactericidal activity against E. coli ML-35 is associated with sequential permeabilization of the OM and IM, and that inner membrane permeabilization appears to be the lethal event.

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Section: Discussionmentioning

confidence: 99%

Interaction of human defensins with Escherichia coli. Mechanism of bactericidal activity.

Lehrer¹,

Barton²,

Daher³

et al. 1989

J. Clin. Invest.

672

516

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“…There are variations in the sequences at the N-and C-termini and in the middle portion of these peptides. These differences have been found to be reflected in their antimicrobial spectrum and specificity of organisms for which they are cidal [14,28]. This functional diversity observed for similarly structured molecules raises interest in identifying the crucial residues responsible for their specificity and antimicrobial potency.…”

Section: Molecular Structure and Antimicrobial Activitymentioning

confidence: 99%

“…Defensins have been isolated from various tissue sources, such as mammalian trachea, intestine, tongue and skin, and human plasma, oral mucosa, salivary glands, saliva and ocular surface [5][6][7][8][9][10][11][12][13]. Defensins are involved in the oxygenindependent mechanism of the host immune response [14]. The `classic' or -defensins were the first group of defensins to be isolated from human and animal phagocytes, and they comprise a large subfamily of polypeptides containing 29-36 residues [3,15].…”

Section: Introductionmentioning

confidence: 99%

Large-scale synthesis and functional elements for the antimicrobial activity of defensins

Raj

Antonyraj

Karunakaran

2000

Biochemical Journal

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Human neutrophil defensins, and their analogues incorporating anionic, hydrophobic or cationic residues at the N- and C-termini, were synthesized by solid-phase procedures. The synthetic defensins were examined for their microbicidal activity against Candida albicans, two Gram-negative bacteria (Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis) and two Gram-positive bacteria (Streptococcus gordonii and Streptococcus mutans). The human neutrophil peptide 1 (HNP1) and HNP2 were found to be potent candidacidal agents. HNP3, which differs by one amino acid at the N-terminus of its sequence, was totally inactive. The Gram-negative bacteria A. actinomycetemcomitans and P. gingivalis and the Gram-positive bacteria S. gordonii and S. mutans were insensitive to human defensins. However, the insertion of two basic residues, such as arginine, at both the N-terminus and the C-terminus of HNP2 significantly enhanced antifungal and antibacterial activity. The addition of anionic residues, such as aspartic acid, at the N- and C-termini rendered the molecule totally inactive. The presence of two hydrophobic amino acids, such as valine, at the N-terminus of HNP2 and of two basic arginine residues at its C-terminus resulted in molecules that were optimally active against these oral pathogens. The results suggest that the N- and C-terminal residues in defensin peptides are the crucial functional elements that determine their microbicidal potency. The three-dimensional structure of all defensins constitutes the same amphiphilic β-sheet structure, with the polar face formed by the N- and C-terminal residues playing an important role in defining microbicidal potency and the antimicrobial spectrum. The enhanced microbicidal activity observed for defensin peptides with two basic residues at both the N- and C-termini could be due to optimization of the amphiphilicity of the structure, which could facilitate specific interactions with the microbial membranes.

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“…Studies have shown consistently that bactericidal activity is independent of these highly conserved features of the peptide family, with the exception of the relatively high Arg content (19,20,25,26,45). Arg residues contribute to Crp4 bactericidal activity, as shown by the loss of function induced in Crp4 by charge reversal or charge neutralization at varied Arg residue positions (36).…”

mentioning

confidence: 99%

Electropositive Charge in α-Defensin Bactericidal Activity: Functional Effects of Lys-for-Arg Substitutions Vary with the Peptide Primary Structure

Llenado¹,

Weeks²,

Cocco³

et al. 2009

Infect Immun

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Cationic amino acids contribute to ␣-defensin bactericidal activity. Curiously, although Arg and Lys have equivalent electropositive charges at neutral pH, ␣-defensins contain an average of nine Arg residues per Lys residue. To investigate the role of high ␣-defensin Arg content, all Arg residues in mouse Paneth cell ␣-defensin cryptdin 4 (Crp4) and rhesus myeloid ␣-defensin 4 (RMAD-4) were replaced with Lys to prepare (R/K)-Crp4 and (R/K)-RMAD-4, respectively. Lys-for-Arg replacements in Crp4 attenuated bactericidal activity and slowed the kinetics of Escherichia coli ML35 cell permeabilization, and (R/K)-Crp4 required longer exposure times to reduce E. coli cell survival. In marked contrast, Lys substitutions in RMAD-4 improved microbicidal activity against certain bacteria and permeabilized E. coli more effectively. Therefore, Arg3Lys substitutions attenuated activity in Crp4 but not in RMAD-4, and the functional consequences of Arg3Lys replacements in ␣-defensins are dependent on the peptide primary structure. In addition, the bactericidal effects of (R/K)-Crp4 and (R/K)-RMAD-4 were more sensitive to inhibition by NaCl than those of the native peptides, suggesting that the high Arg content of ␣-defensins may be under selection to confer superior microbicidal function under physiologic conditions.

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Oxygen-Independent Bactericidal Systems: Mechanisms and Disorders

Cited by 36 publications

References 47 publications

Interaction of human defensins with Escherichia coli. Mechanism of bactericidal activity.

Interaction of human defensins with Escherichia coli. Mechanism of bactericidal activity.

Large-scale synthesis and functional elements for the antimicrobial activity of defensins

Electropositive Charge in α-Defensin Bactericidal Activity: Functional Effects of Lys-for-Arg Substitutions Vary with the Peptide Primary Structure

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