18 research outputs found
Antimicrobial Peptides in 2014.
This article highlights new members, novel mechanisms of action, new functions, and interesting applications of antimicrobial peptides reported in 2014. As of December 2014, over 100 new peptides were registered into the Antimicrobial Peptide Database, increasing the total number of entries to 2493. Unique antimicrobial peptides have been identified from marine bacteria, fungi, and plants. Environmental conditions clearly influence peptide activity or function. Human α-defensin HD-6 is only antimicrobial under reduced conditions. The pH-dependent oligomerization of human cathelicidin LL-37 is linked to double-stranded RNA delivery to endosomes, where the acidic pH triggers the dissociation of the peptide aggregate to release its cargo. Proline-rich peptides, previously known to bind to heat shock proteins, are shown to inhibit protein synthesis. A model antimicrobial peptide is demonstrated to have multiple hits on bacteria, including surface protein delocalization. While cell surface modification to decrease cationic peptide binding is a recognized resistance mechanism for pathogenic bacteria, it is also used as a survival strategy for commensal bacteria. The year 2014 also witnessed continued efforts in exploiting potential applications of antimicrobial peptides. We highlight 3D structure-based design of peptide antimicrobials and vaccines, surface coating, delivery systems, and microbial detection devices involving antimicrobial peptides. The 2014 results also support that combination therapy is preferred over monotherapy in treating biofilms
Antimicrobial Peptides in 2014
This article highlights new members, novel mechanisms of action, new functions, and interesting applications of antimicrobial peptides reported in 2014. As of December 2014, over 100 new peptides were registered into the Antimicrobial Peptide Database, increasing the total number of entries to 2493. Unique antimicrobial peptides have been identified from marine bacteria, fungi, and plants. Environmental conditions clearly influence peptide activity or function. Human α-defensin HD-6 is only antimicrobial under reduced conditions. The pH-dependent oligomerization of human cathelicidin LL-37 is linked to double-stranded RNA delivery to endosomes, where the acidic pH triggers the dissociation of the peptide aggregate to release its cargo. Proline-rich peptides, previously known to bind to heat shock proteins, are shown to inhibit protein synthesis. A model antimicrobial peptide is demonstrated to have multiple hits on bacteria, including surface protein delocalization. While cell surface modification to decrease cationic peptide binding is a recognized resistance mechanism for pathogenic bacteria, it is also used as a survival strategy for commensal bacteria. The year 2014 also witnessed continued efforts in exploiting potential applications of antimicrobial peptides. We highlight 3D structure-based design of peptide antimicrobials and vaccines, surface coating, delivery systems, and microbial detection devices involving antimicrobial peptides. The 2014 results also support that combination therapy is preferred over monotherapy in treating biofilms
Sequence Permutation Generates Peptides with Different Antimicrobial and Antibiofilm Activities
Antibiotic resistance poses a threat to our society, and 10 million people could die by 2050. To design potent antimicrobials, we made use of the antimicrobial peptide database (APD). Using the database filtering technology, we identified a useful template and converted it into an effective peptide WW291 against methicillin-resistant Staphylococcus aureus (MRSA). Here, we compared the antibacterial activity and cytotoxicity of a family of peptides obtained from sequence permutation of WW291. The resulting eight WW peptides (WW291-WW298) gained different activities against a panel of bacteria. While WW295 inhibited the growth of Escherichia coli, WW298 was highly active against S. aureus USA300 LAC. Consistently with this, WW298 was more effective in permeating or depolarizing the S. aureus membranes, whereas WW295 potently permeated the E. coli membranes. In addition, WW298, but not WW295, inhibited the MRSA attachment and could disrupt its preformed biofilms more effectively than daptomycin. WW298 also protected wax moths Galleria mellonella from MRSA infection causing death. Thus, sequence permutation provides one useful avenue to generating antimicrobial peptides with varying activity spectra. Taken together with amino acid composition modulation, these methods may lead to narrow-spectrum peptides that are more promising to selectively eliminate invading pathogens without damaging commensal microbiota
The π Configuration of the WWW Motif of a Short Trp-Rich Peptide Is Critical for Targeting Bacterial Membranes, Disrupting Preformed Biofilms, and Killing Methicillin-Resistant <i>Staphylococcus aureus</i>
Tryptophan-rich peptides,
being short and suitable for large-scale
chemical synthesis, are attractive candidates for developing a new
generation of antimicrobials to combat antibiotic-resistant bacteria
(superbugs). Although there are numerous pictures of the membrane-bound
structure of a single tryptophan (W), how multiple Trp amino acids
assemble themselves and interact with bacterial membranes is poorly
understood. This communication presents the three-dimensional structure
of an eight-residue Trp-rich peptide (WWWÂLÂRÂKIW-NH<sub>2</sub> with 50% W) determined by the improved two-dimensional nuclear
magnetic resonance method, which includes the measurements of <sup>13</sup>C and <sup>15</sup>N chemical shifts at natural abundance.
This peptide forms the shortest two-turn helix with a distinct amphipathic
feature. A unique structural arrangement is identified for the Trp
triplet, WWW, that forms a π configuration with W2 as the horizontal
bar and W1/W3 forming the two legs. An arginine scan reveals that
the WWW motif is essential for killing methicillin-resistant <i>Staphylococcus aureus</i> USA300 and disrupting preformed bacterial
biofilms. This unique π configuration for the WWW motif is stabilized
by aromatic–aromatic interactions as evidenced by ring current
shifts as well as nuclear Overhauser effects. Because the WWW motif
is maintained, a change of I7 to R led to a potent antimicrobial and
antibiofilm peptide with 4-fold improvement in cell selectivity. Collectively,
this study elucidated the structural basis of antibiofilm activity
of the peptide, identified a better peptide candidate via structure–activity
relationship studies, and laid the foundation for engineering future
antibiotics based on the WWW motif
Anti-Staphylococcal Biofilm Effects of Human Cathelicidin Peptides
<i>Staphylococcus aureus</i> can live together in the
form of biofilms to avoid elimination by the host. Thus, a useful
strategy to counteract bacterial biofilms is to re-engineer human
antimicrobial peptide LL-37 so that it can be used as a remedy for
preventing and removing biofilms. This study reports antibiofilm effects
of four human cathelicidin LL-37 peptides against community-associated
and hospital isolated methicillin-resistant <i>Staphylococcus
aureus</i> (MRSA) strains. Although the intact molecule LL-37
inhibited biofilm formation at low concentrations, it did not inhibit
bacterial attachment nor disrupt preformed biofilms. However, two
17-residue peptides, GF-17 and 17BIPHE2, inhibited bacterial attachment,
biofilm growth, and disrupted established biofilms. An inactive peptide
RI-10 was used as a negative control. Our results obtained using the <i>S. aureus</i> mutants in a static biofilm model are consistent
with the literature obtained in a flow cell biofilm model. Because
17BIPHE2 is the most effective biofilm disruptor with desired stability
to proteases, it is a promising lead for developing new anti-MRSA
biofilm agents
Low cationicity is important for systemic in vivo efficacy of database-derived peptides against drug-resistant Gram-positive pathogens
Peptide Stability Is Important but Not a General Requirement for Antimicrobial and Antibiofilm Activity In Vitro and In Vivo
Peptide stability to proteases has
been a major requirement for
developing peptide therapeutics. This study investigates the effects
of peptide stability on antimicrobial and antibiofilm activity under
various conditions. For this purpose, two human cathelicidin-derived
peptides differing in stability to proteases were utilized. While
GF-17, a peptide derived from the major antimicrobial region of human
LL-37, can be rapidly cleaved by proteases, the engineered peptide
17BIPHE2 is resistant to multiple proteases. In the standard antimicrobial
susceptibility, killing kinetics, and membrane permeabilization assays
conducted in vitro using planktonic bacteria, these two peptides displayed
similar potency. The two peptides were also similarly active against
methicillin-resistant Staphylococcus aureus (MRSA) USA300 prior to biofilm formation. However, 17BIPHE2 was
superior to GF-17 in disrupting preformed biofilms probably due to
both enhanced stability and slightly higher DNA binding capacity.
In a wax moth model, 17BIPHE2 better protected insects from MRSA infection-caused
death than GF-17, consistent with the slower degradation of 17BIPHE2
than GF-17. Here, peptide antimicrobial activity was found to be critical
for in vivo efficacy. When incorporated in the nanofiber/microneedle
delivery device, GF-17 and 17BIPHE2 displayed a similar effect in
eliminating MRSA in murine chronic wounds, underscoring the advantage
of nanofibers in protecting the peptide from degradation. Since nanoformulation
can ease the requirement of peptide stability, it opens the door to
a direct use of natural peptides or their cocktails for antimicrobial
treatment, accelerating the search of effective antibiofilm peptides
to treat chronic wounds
Transformation of Human Cathelicidin LL-37 into Selective, Stable, and Potent Antimicrobial Compounds
This Letter reports a family of novel
antimicrobial compounds obtained
by combining peptide library screening with structure-based design.
Library screening led to the identification of a human LL-37 peptide
resistant to chymotrypsin. This d-amino-acid-containing peptide
template was active against <i>Escherichia coli</i> but
not methicillin-resistant <i>Staphylococcus aureus</i> (MRSA).
It possesses a unique nonclassic amphipathic structure with hydrophobic
defects. By repairing the hydrophobic defects, the peptide (17BIPHE2)
gained activity against the ESKAPE pathogens, including <i>Enterococcus
faecium, S. aureus, Klebsiella pneumoniae, Acinetobacter baumanii,
Pseudomonas aeruginosa</i>, and <i>Enterobacter</i> species. <i>In vitro</i>, 17BIPHE2 could disrupt bacterial
membranes and bind to DNA. <i>In vivo</i>, the peptide prevented
staphylococcal biofilm formation in a mouse model of catheter-associated
infection. Meanwhile, it boosted the innate immune response to further
combat the infection. Because these peptides are potent, cell-selective,
and stable to several proteases, they may be utilized to combat one
or more ESKAPE pathogens
Two distinct amphipathic peptide antibiotics with systemic efficacy.
Antimicrobial peptides are important candidates for developing new classes of antibiotics because of their potency against antibiotic-resistant pathogens. Current research focuses on topical applications and it is unclear how to design peptides with systemic efficacy. To address this problem, we designed two potent peptides by combining database-guided discovery with structure-based design. When bound to membranes, these two short peptides with an identical amino acid composition can adopt two distinct amphipathic structures: A classic horizontal helix (horine) and a novel vertical spiral structure (verine). Their horizontal and vertical orientations on membranes were determined by solid-stat