Membrane Active Peptides

Nisin is a bacteriocin which is produced by Lactococcus lactis and approved by FDA to be utilized as GRAS status food additive. Nisin has antimicrobial activity against Listeria, Clostridium, Staphylococcus and Bacillus species or spores. Also it some circumtances, it has an immune modulator role and a selective cytotoxic effect against cancer cells. However, it is notable that the high production cost of nisin is an important issue which restricts its intensively use. The major reason is the low nisin production yield of producer strains. In recent years, the production of nisin has been significantly improved by genetic modifications in nisin producer strains or also innovative applications in fermentation conditions. Recently, 15400 IU/mL nisin production has been achieved in L. lactis cells by genetic modifications with eliminating the factors that affect nisin biosynthesis or by increasing the density of the producing strains in the fermentation medium. In this review, the innovative approaches, which were applied in cell and fermentation systems where nisin production is increased, are comparatively discussed and interpreted regarding developing industrial nisin production.

Cell-penetrating peptides (CPPs) and antimicrobial peptides (AMPs) are generally defined as small cationic peptides with the ability to interact with lipidic membranes, in a process driven by electrostatic and hydrophobic processes. The interaction with CPPs is known to lead to its translocation across the membrane, while with AMPs lead to membrane damage. Here we present one synthetic anionic peptide, LE10 (LELELELELELELELELELE), which strongly interacts with model membranes, showing properties of CPPs (translocation through lipidic membranes on a mechanism usually described for cationic CPPs) and AMPs (membrane disruption) in molecular dynamic studies, experimental studies with liposomes and mammalian cells in vitro. Based on the LE10 properties here demonstrated, small modifications in its structure could make it a very promising tool for drug delivery.

Life-threatening infectious diseases are on their way to cause a worldwide crisis, as treating them effectively is becoming increasingly difficult due to the emergence of antibiotic resistant strains. Antimicrobial peptides (AMPs) form an ancient type of innate immunity found universally in all living organisms, providing a principal first-line of defense against the invading pathogens. The unique diverse function and architecture of AMPs has attracted considerable attention by scientists, both in terms of understanding the basic biology of the innate immune system, and as a tool in the design of molecular templates for new anti-infective drugs. 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 have been subject of natural evolution, as have the microbes, for hundreds of millions of years. Despite this long history of co-evolution, AMPs have not lost their ability to kill or inhibit the microbes totally, nor have the microbes learnt to avoid the lethal punch of AMPs. AMPs therefore have potential to provide an important break through and form the basis for a new class of antibiotics. In this review, we would like to give an overview of cationic antimicrobial peptides, origin, structure, functions, and mode of action of AMPs, which are highly expressed and found in humans, as well as a brief discussion about widely abundant, well characterized AMPs in mammals, in addition to pharmaceutical aspects and additional functions of AMPs.

The physiological and pathological roles of nascent amyloid beta (Aβ) monomers are still debated in the literature. Their involvement in the pathological route of Alzheimer’s Disease (AD) is currently considered to be the most relevant, triggered by their aggregation into structured oligomers, a toxic species. Recently, it has been suggested that nascent Aβ, out of the amyloidogenic pathway, plays a physiological and protective role, especially in the brain. In this emerging perspective, the study presented in this paper investigated whether the organization of model membranes is affected by contact with Aβ in the nascent state, as monomers. The outcome is that, notably, the rules of engagement and the resulting structural outcome are dictated by the composition and properties of the membrane, rather than by the Aβ variant. Interestingly, Aβ monomers are observed to favor the tightening of adjacent complex membranes, thereby affecting a basic structural event for cell-cell adhesion ...

Background: Lantibiotics are small lanthionine-containing bacteriocins produced by lactic acid bacteria. Salivaricin 9 is a newly discovered lantibiotic produced by Streptococcus salivarius. In this study we present the mechanism of action of salivaricin 9 and some of its properties. Also we developed new methods to produce and purify the lantibiotic from strain NU10. Methodology / Principal Findings: Salivaricin 9 was found to be auto-regulated when an induction assay was applied and this finding was used to develop a successful salivaricin 9 production system in liquid medium. A combination of XAD-16 and cation exchange chromatography was used to purify the secondary metabolite which was shown to have a molecular weight of approximately 3000 Da by SDS-PAGE. MALDI-TOF MS analysis indicated the presence of salivaricin 9, a 2560 Da lantibiotic. Salivaricin 9 is a bactericidal molecule targeting the cytoplasmic membrane of sensitive cells. The membrane permeabilization assay showed that salivaricin 9 penetrated the cytoplasmic membrane and induced pore formation which resulted in cell death. The morphological changes of test bacterial strains incubated with salivaricin 9 were visualized using Scanning Electron Microscopy which confirmed a pore forming mechanism of inhibition. Salivaricin 9 retained biological stability when exposed to high temperature (90-100°C) and stayed bioactive at pH ranging 2 to 10. When treated with proteinase K or peptidase, salivaricin 9 lost all antimicrobial activity, while it remained active when treated with lyticase, catalase and certain detergents. Conclusion: The mechanism of antimicrobial action of a newly discovered lantibiotic salivaricin 9 was elucidated in this study. Salivaricin 9 penetrated the cytoplasmic membrane of its targeted cells and induced pore formation. This project has given new insights on lantibiotic peptides produced by S. salivarius isolated from the oral cavities of Malaysian subjects.

Resistance to conventional antimicrobials is burgeoning. Consequently, the world health has mandated researchers to develop novel antimicrobial agents as replacement for conventional antimicrobials. Of the potential alternatives, bacteriocins are widely considered lead compounds. Salivaricin mmaye1 and pentocin MQ1 are bacteriocins produced by Lactobacillus salivarius SPW1 and Lactobacillus pentosus CS2 respectively. These bacteriocins have been reported to possess high antimicrobial activity against human pathogens. The overall objective of this study is to optimize production of salivaricin mmaye1 and evaluate its potential synergistic action with pentocin MQ1. Results revealed that Lactobacillus salivarius SPW1 is non-hemolytic and sensitive to most antibiotics screened but resistant to gentamicin, streptomycin and vancomycin. Resistance to these antibiotics is not mediated by plasmids. Genes encoding salivaricin mmaye1 production are not plasmid-borne. A new medium for high biom...

Resistance to conventional antimicrobials is burgeoning. Consequently, the world health has mandated researchers to develop novel antimicrobial agents as replacement for conventional antimicrobials. Of the potential alternatives, bacteriocins are widely considered lead compounds. Salivaricin mmaye1 and pentocin MQ1 are bacteriocins produced by Lactobacillus salivarius SPW1 and Lactobacillus pentosus CS2 respectively. These bacteriocins have been reported to possess high antimicrobial activity against human pathogens. The overall objective of this study is to optimize production of salivaricin mmaye1 and evaluate its potential synergistic action with pentocin MQ1. Results revealed that Lactobacillus salivarius SPW1 is non-hemolytic and sensitive to most antibiotics screened but resistant to gentamicin, streptomycin and vancomycin. Resistance to these antibiotics is not mediated by plasmids. Genes encoding salivaricin mmaye1 production are not plasmid-borne. A new medium for high biom...

Background

Lantibiotics are small lanthionine-containing bacteriocins produced by lactic acid bacteria. Salivaricin 9 is a newly discovered lantibiotic produced by Streptococcus salivarius. In this study we present the mechanism of action of salivaricin 9 and some of its properties. Also we developed new methods to produce and purify the lantibiotic from strain NU10.

Methodology / Principal Findings

Salivaricin 9 was found to be auto-regulated when an induction assay was applied and this finding was used to develop a successful salivaricin 9 production system in liquid medium. A combination of XAD-16 and cation exchange chromatography was used to purify the secondary metabolite which was shown to have a molecular weight of approximately 3000 Da by SDS-PAGE. MALDI-TOF MS analysis indicated the presence of salivaricin 9, a 2560 Da lantibiotic. Salivaricin 9 is a bactericidal molecule targeting the cytoplasmic membrane of sensitive cells. The membrane permeabilization assay showed that salivaricin 9 penetrated the cytoplasmic membrane and induced pore formation which resulted in cell death. The morphological changes of test bacterial strains incubated with salivaricin 9 were visualized using Scanning Electron Microscopy which confirmed a pore forming mechanism of inhibition. Salivaricin 9 retained biological stability when exposed to high temperature (90-100°C) and stayed bioactive at pH ranging 2 to 10. When treated with proteinase K or peptidase, salivaricin 9 lost all antimicrobial activity, while it remained active when treated with lyticase, catalase and certain detergents.

Conclusion

The mechanism of antimicrobial action of a newly discovered lantibiotic salivaricin 9 was elucidated in this study. Salivaricin 9 penetrated the cytoplasmic membrane of its targeted cells and induced pore formation. This project has given new insights on lantibiotic peptides produced by S. salivarius isolated from the oral cavities of Malaysian subjects.

Lantibiotics are small lanthionine-containing bacteriocins produced by lactic acid bacteria. Salivaricin 9 is a newly discovered lantibiotic produced by Streptococcus salivarius. In this study we present the mechanism of action of salivaricin 9 and some of its properties. Also we developed new methods to produce and purify the lantibiotic from strain NU10.

Motivation: The evolution of multicellular organisms is associated with increasing variability of molecules governing behavioral and physiological states. This is often achieved by Neuropeptides (NPs) that are produced in neurons from a longer protein, named neuropeptide precursor (NPP). The maturation of NPs occurs through a sequence of proteolytic cleavages. The difficulty in identifying NPPs is a consequence of their diversity and the lack of applicable sequence similarity among the short, functionally related NPs. Results: Herein, we describe NeuroPID, a machine-learning scheme that predicts Metazoan NPPs. NeuroPID was trained on hundreds of identified NPPs from the UniProtKB database. Some 600 features were extracted from the primary sequences and processed using support vector machines (SVM) and ensemble decision tree classifiers. These features combined biophysical, chemical and informational-statistical properties of NPs and NPPs. Other features were guided by the defining characteristics of the dibasic cleavage sites motif. NeuroPID reached 89-94% accuracy and 90-93% precision in cross-validation blind tests against known NPPs (with an emphasis on Chordata and Arthropoda). NeuroPID also identified NPP-like proteins from extensively studied model organisms as well as from poorly annotated proteomes. We then focused on the most significant sets of features that contribute to the success of the classifiers. We propose that NPPs are attractive targets for investigating and modulating behavior, metabolism and homeostasis, and that a rich repertoire of NPs remains to be identified. Availability: NeuroPID source code is freely available at