Effect of Selectively Introducing Arginine and D-Amino Acids on the Antimicrobial Activity and Salt Sensitivity in Analogs of Human Beta-Defensins

Olli, Sudar; Rangaraj, Nandini; Nagaraj, Ramakrishnan

doi:10.1371/journal.pone.0077031

Cited by 19 publications

(11 citation statements)

References 54 publications

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“…However, the R/K ratio is variable, as is the number of R and K residues. R residues play an important role in modulating the activity of defensins (40)(41)(42)(43). Hence, a hybrid peptide containing the C-terminal K-rich segment of HBD-1 and the R-rich domain of -defensin was designed and synthesized.…”

Section: Resultsmentioning

confidence: 99%

A Hybrid Cationic Peptide Composed of Human β-Defensin-1 and Humanized θ-Defensin Sequences Exhibits Salt-Resistant Antimicrobial Activity

Olli

Nagaraj

Motukupally

2015

Antimicrob Agents Chemother

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We have designed a hybrid peptide by combining sequences of human ␤-defensin-1 (HBD-1) and -defensin, in an attempt to generate a molecule that combines the diversity in structure and biological activity of two different peptides to yield a promising therapeutic candidate. HBD-1 was chosen as it is a natural defensin of humans that is constitutively expressed, but its antibacterial activity is considerably impaired by elevated ionic strength. -Defensins are expressed in human bone marrow as a pseudogene and are homologous to rhesus monkey circular minidefensins. Retrocyclins are synthetic human -defensins. The cyclic nature of the -defensin peptides makes them salt resistant, nonhemolytic, and virtually noncytotoxic in vitro. However, a nonhuman circular molecule developed for clinical use would be less viable than a linear molecule. In this study, we have fused the C-terminal region of HBD-1 to the nonapeptide sequence of a synthetic retrocyclin. Cyclization was achieved by joining the terminal ends of the hybrid peptide by a disulfide bridge. The hybrid peptide with or without the disulfide bridge exhibited enhanced antimicrobial activity against both Gram-negative and Gram-positive bacteria as well as against fungi, including clinical bacterial isolates from eye infections. The peptide retained activity in the presence of NaCl and serum and was nonhemolytic in vitro. Thus, the hybrid peptide generated holds potential as a new class of antibiotics. Defensins are a group of peptides that are important components of host defense. They have the ability to recognize and neutralize invading microorganisms quickly and specifically (1-3). These peptides are diverse members of a large family of cationic host defense peptides (HDPs) that are widely distributed throughout the animal kingdom (2, 4, 5). These cysteine-rich peptides vary in their length, the spacing of their cysteine residues, and their disulfide connectivities (4, 5). Defensins show antimicrobial activities against Gram-negative and Gram-positive bacterial strains, fungi, as well as some parasites and enveloped viruses (1, 2, 4, 6). Mammalian defensins can be classified into ␣-, ␤-, and -defensins on the basis of their disulfide connectivities (2, 4, 6-8).Only ␣-and ␤-defensins are expressed in humans. -Defensin (found in rhesus monkey) displays the same connectivity associated with that of the ␣-defensins but is not functionally present in humans (7). -Defensins are much smaller (18 amino acid residues) than ␣-and ␤-defensins (29 to 45 residues), and their antiviral properties are considerably more pronounced than their antibacterial and antifungal effects (9, 10).␤-Defensins are found in epithelial cells that line mucosal surfaces and that provide the first line of defense between an organism and the environment (2, 6). To date, four human ␤-defensins (human ␤-defensin-1 [HBD-1] to HBD-4) have been characterized (5,(11)(12)(13)(14)(15)(16)(17)(18)(19). HBD-1 is expressed in epithelia that are directly exposed to the environment or microbial flora (e.g.,...

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Section: Resultsmentioning

confidence: 99%

A Hybrid Cationic Peptide Composed of Human β-Defensin-1 and Humanized θ-Defensin Sequences Exhibits Salt-Resistant Antimicrobial Activity

Olli

Nagaraj

Motukupally

2015

Antimicrob Agents Chemother

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“…These effects are complex and difficult to computationally model, for the ‘consequences of the substitution of arginines for lysines is also modulated by the nature of the peptide into which the substitution is made’ 14 . Such substitutions (applied to β -defensins also, and not AH peptides) also hold promise as future therapeutic drugs 29 .…”

Section: Resultsmentioning

confidence: 99%

PAGAL - Properties and corresponding graphics of alpha helical structures in proteins

2014

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Alpha helices (AH) are peptide fragments characterized by regular patterns of hydrogen bonding between the carbonyl oxygen and amino nitrogen of residues regularly spaced in sequence, resulting in spiral conformations. Their preponderance in protein structures underlines their importance. Interestingly, AHs are present in most anti-microbial peptides, although they might remain in random-coil conformations depending on the solvent dielectric. For example, the cecropin component of the chimeric anti-microbial protein designed previously by our group comprises of two AHs linked by a short stretch of random coil. These anti-microbial peptides are often amphipathic (quantified by a hydrophobic moment), aligning hydrophobic residues on one surface and charged residues on the others. In the current work, we reproduce previously described computational methods to compute the hydrophobic moment of AHs - and provide open access to the source code (PAGAL). We simultaneously generated input files for TikZ (a package for creating high resolution graphics programmatically) to obtain the Edmundson wheel and showing the direction and magnitude of the hydrophobic moment, and Pymol scripts to generate color coded protein surfaces. Additionally, we have observed an empirical structural property of AHs: the distance between the Cα atoms of the ith and (i+4)th residue is equal to the distance between the carbonyl oxygens of the ith and (i+4)th residue. We validated this using 100 non-homologous high resolution structures from the PISCES database. The source code and manual is available at http://github.com/sanchak/pagal and on http://dx.doi.org/10.5281/zenodo.11136.

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“…Ala scanning mutagenesis revealed that for HNP1 (Wei et al, 2010) and HD5 (de Leeuw et al, 2009; Rajabi et al, 2012) the decrease in hydrophobicity is functionally more deleterious than decrease in net cationicity, yet the latter certainly is the essential component of the defensins’ functionality. Higher cationicity in general, and higher arginine content in particular, appear to correlate with higher salt resistance and higher antimicrobial potential for both α- and β-defensins (Llenado et al, 2009; Mathew and Nagaraj, 2015; Olli et al, 2013; Wang et al, 2015; Zou et al, 2007). Yet, the net cationicity does not appear to correlate well with the antitoxin activities of defensins as moderately basic α-defensins HNP1–3 (pI 8.3–8.7) are substantially more potent against most tested toxins than β-defensins hBD1–3 (pI 8.9–10.1) and therefore additional parameters must be considered.…”

Section: Common Features Of Toxins and Inactivation Mechanisms By Defmentioning

confidence: 99%

Targeting and inactivation of bacterial toxins by human defensins

Kudryashova

Seveau

Kudryashov

2017

Biological Chemistry

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Defensins as a prominent family of antimicrobial peptides (AMP) are major effectors of the innate immunity with a broad range of immune modulatory and antimicrobial activities. Particularly, defensins are the only recognized fast-response molecules that can neutralize a broad range of bacterial toxins, many of which are among the deadliest compounds on the planet. For a decade, the mystery of how a small and structurally conserved group of peptides can neutralize a heterogeneous group of toxins with little to no sequential and structural similarity remained unresolved. Recently, it was found that defensins recognize and target structural plasticity/thermodynamic instability, fundamental physicochemical properties that unite many bacterial toxins and distinguish them from the majority of host proteins. Binding of human defensins promotes local unfolding of the affected toxins, destabilizes their secondary and tertiary structures, increases susceptibility to proteolysis, and leads to their precipitation. While the details of toxin destabilization by defensins remain obscure, here we briefly review properties and activities of bacterial toxins known to be affected by or to be resilient to defensins and discuss how recognized features of defensins correlate with the observed inactivation.

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Effect of Selectively Introducing Arginine and D-Amino Acids on the Antimicrobial Activity and Salt Sensitivity in Analogs of Human Beta-Defensins

Cited by 19 publications

References 54 publications

A Hybrid Cationic Peptide Composed of Human β-Defensin-1 and Humanized θ-Defensin Sequences Exhibits Salt-Resistant Antimicrobial Activity

A Hybrid Cationic Peptide Composed of Human β-Defensin-1 and Humanized θ-Defensin Sequences Exhibits Salt-Resistant Antimicrobial Activity

PAGAL - Properties and corresponding graphics of alpha helical structures in proteins

Targeting and inactivation of bacterial toxins by human defensins

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