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Biomolecules as host defense weapons against microbial pathogens
Abstract and Figures
Antimicrobial peptides have been considered a new source of biomolecules in several fields of research/innovative applications: they would adjust to an ideal behavior seeking to overcome clinician, microbiological, human-animal-plant-environmental concerns. Antimicrobial peptides can be considered as ancient weapons found in living organisms suggesting they have played a fundamental role in his successful co-evolution with pathogens. Acting on microorganism membrane or having intracellular targets, they can also act as effectors of the innate immune response resulting on non-specific mechanisms of action. Two elements have speeded the research on pathogen control alternatives: a verified increase of antibiotic resistance and the relevance of finding amenable environmental compounds in plant health. As a result of its importance, great efforts have been accomplished to find, characterize, combine and synthesize effective antimicrobial peptides. This review intends to emphasize the generation of biomolecules, whether native or synthetic analogues, that have been matter of recent patents. Development of biomolecules suitable for therapeutic scopes and agricultural use have several challenges such as intrinsic toxicity, in vivo stability and suitable formulation contemplating the cost of production. Thus, biotechnological procedures using microbial systems or transgenic crops as plant factories might help to solve these challenges.
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... It was studied that antimicrobial peptides are the major source that provides defense against pathogens. Although the defense provided by these antimicrobial peptides is one of the ancient type of system, but this system found to be evolved in relation to the pathogens [22]. The following figure 1 show some of the bio-molecules involve in driving the co-evolutionary process fast. ...
Background: Co-evolution of human and microbial genome is of fundamental interest. It allows both the human and pathogens to adapt themselves in the changing environment. Even in an experimental condition to check resistance against a particular antibiotic the microbes slowly develop resistance against that antibiotic in laboratory environment. Thus it is a very critical issue that should be address in order to overcome the microbial diseases. Purpose: The present study is focus on the currently evolved pathogens and availability of vaccines; that work against the pathogens to protect human population. Conclusion: By understanding the way pathogens get evolved will be helpful in future to develop new and more affective vaccines. It may also helpful in understanding the disease pathogenesis.
Aims:
Crotalicidin (Ctn), a cathelicidin-related antimicrobial peptide from the South American rattlesnake venom gland, and its C-terminal Ctn[15-34] fragment, have shown important activities against microorganisms, trypanosomatid protozoa and certain lines of tumor cells. Herein, the activity against clinical strains of fluconazole-resistant Candida albicans and of amphotericin B and fluconazole-resistant Cryptococcus neoformans was investigated.
Methods and results:
Microdilution and luminescent cell viability tests were used to evaluate and compare the susceptibility of pathogenic yeasts to these peptides. The time-kill curves of the most active Ctn[15-34] alone or in combination with fluconazole against drug-resistant yeasts were determined. Concomitantly, the fungicidal and/or fungistatic effects of Ctn[15-34] were visualized by the spotting test. The peptides were active against all strains, including those resistant to antifungals. The association of fluconazole with both Ctn and Ctn[15-34], although not synergic, was additive. In contrast, such pattern was not observed for C. neoformans.
Conclusions:
Overall, Ctn and Ctn[15-34] are potential antifungal leads displaying anti-yeast activities against clinical isolates endowed with drug resistance mechanisms.
Significance and impact of the study:
The effective peptide activity against resistant strains of pathogenic yeasts demonstrates that crotalicidin-derived peptides are promising templates to develop new antifungal pharmaceuticals.
Temporins are a novel family of small (10–13 residues) cationic antimicrobial peptides recently isolated from the skin of the European red frog Rana temporaria. Although recently acquired evidence shows that temporins have the potential to kill bacteria by permeabilizing the cytoplasmic membrane, the molecular mechanisms of membrane selectivity and permeabilization are largely unknown. In this study, it was found that temporins cause the release of fluorescent markers entrapped in phosphatidylcholine liposomes in a manner that depends significantly on the size of the solute. Temporins were also shown to lack a detergent-like effect on lipid vesicles, indicating that marker leakage caused by these peptides is not due to total membrane disruption but to perturbation of bilayer organization on a local scale. Binding of temporins to liposomes did lead to a small increase in lipid hydrocarbon chain mobility, as revealed by EPR spectroscopy of nitroxide-labeled fatty acids incorporated in the bilayer. Reference experiments were conducted using the bee venom peptide melittin, whose properties and behavior in natural and model membrane systems are well known. Our findings for temporins are discussed in relation to the models proposed to date to account for the action of antimicrobial peptides on membranes.
The antimicrobial properties of the cyclic -sheet peptide gramicidin S are attributed to its destabilizing effect on lipid membranes. Here we present the membrane-bound structure and alignment of a derivative of this peptide, based on angular and distance constraints. Solid-state 19F-NMR was used to study a 19F-labelled gramicidin S analogue in dimyristoylphosphatidylcholine bilayers at a lipid:peptide ratio of 80:1 and above. Two equivalent leucine side chains were replaced by the non-natural amino acid 4F-phenylglycine, which serves as a highly sensitive reporter on the structure and dynamics of the peptide backbone. Using a modified CPMG multipulse sequence, the distance between the two 19F-labels was measured from their homonuclear dipolar coupling as 6, in good agreement with the known backbone structure of natural gramicidin S in solution. By analyzing the anisotropic chemical shift of the 19F-labels in macroscopically oriented membrane samples, we determined the alignment of the peptide in the bilayer and described its temperature-dependent mobility. In the gel phase, the 19F-labelled gramicidin S is aligned symmetrically with respect to the membrane normal, i.e., with its cyclic -sheet backbone lying flat in the plane of the bilayer, which is fully consistent with its amphiphilic character. Upon raising the temperature to the liquid crystalline state, a considerable narrowing of the 19F-NMR chemical shift dispersion is observed, which is attributed the onset of global rotation of the peptide and further wobbling motions. This study demonstrates the potential of the 19F nucleus to describe suitably labelled polypeptides in membranes, requiring only little material and short NMR acquisition times.
Although seeds have been the subject of extensive studies for many years, their seed coats are just beginning to be examined
from the perspective of molecular genetics and control of development. The seed coat, plays a vital role in the life cycle
of plants by controlling the development of the embryo and determining seed dormancy and germination. Within the seed coat
are a number of unique tissues that undergo differentiation to serve specific functions in the seed. A large number of genes
are known to be specifically expressed within the seed coat tissues; however, very few of them are understood functionally.
The seed coat synthesizes a wide range of novel compounds that may serve the plant in diverse ways, including defense and
control of development. Many of the compounds are sources of industrial products and are components of food and feeds. The
use of seed coat biotechnology to enhance seed quality and yield, or to generate novel components has not been exploited,
largely because of lack of knowledge of the genetic systems that govern seed coat development and composition. In this review,
we will examine the recent advances in seed coat, biology from the perspective of structure, composition and molecular genetics.
We will consider the diverse avenues that are possible for seed coat biotechnology in the future. This review will focus principally
on the seed coats of the Brassicaceae and Fabaceae as they allow us to merge the areas of molecular biology, physiology and structure to gain a perspective on the possibilities
for seed coat modifications in the future.
Antibiotic resistance is increasing at a rate that far exceeds the pace of new development of drugs. Antimicrobial peptides,
both synthetic and from natural sources, have raised interest as pathogens become resistant against conventional antibiotics.
Indeed, one of the major strengths of this class of molecules is their ability to kill multidrug-resistant bacteria. Antimicrobial
peptides are relatively small (6 to 100 aminoacids), amphipathic molecules of variable length, sequence and structure with
activity against a wide range of microorganisms including bacteria, protozoa, yeast, fungi, viruses and even tumor cells.
They usually act through relatively non-specific mechanisms resulting in membranolytic activity but they can also stimulate
the innate immune response. Several peptides have already entered pre-clinical and clinical trials for the treatment of catheter
site infections, cystic fibrosis, acne, wound healing and patients undergoing stem cell transplantation. We review the advantages
of these molecules in clinical applications, their disadvantages including their low in vivo stability, high costs of production and the strategies for their discovery and optimization.
A large group of low molecular weight natural compounds that exhibit antimicrobial activity has been isolated from animals and plants during the past two decades. Among them, cationic peptides are the most widespread. Interestingly, the variety and diversity of these peptides seem to be much wider than suspected. In fact, novel classes of peptides with varying chemical propertiescontinue to be isolated from different vertebrate and invertebrate species, as well as from bacteria. To the early characterized peptides, mostly cationic in nature, anionic peptides, aromatic dipeptides, processed forms of oxygen-binding proteins and processed forms of natural structural and functional proteins can now be added, just to name a few. In spite of the astonishing diversity in structure and chemical nature displayed by these molecules, all of them present antimicrobial activity, a condition that has led researchers to consider them as "natural antibiotics" and as such a new and innovative alternative to chemical antibiotics with a promising future as biotechnological tools. A resulting new generation of anti microbial peptides (AMPs) with higher specific activity and wider microbe-range of action could be constructed, and hopefully endogenously expressed in genetically-modified organisms.
Antifungal peptides have been identified in a wide range of life forms which include plants, mammals, and microorganism. Their structure are as varied as their antifungal properties. Semisynthetic and fully synthetic analogs have been developed from a few of these natural peptides that are superior to the paren compound. A few of these peptides hold promise in combating fungal infections and have entered clinical trials.
Antimicrobial peptides (AMPs) that assume an amphipathic α helical structure are widespread in nature. Their activity depends on several parameters including the sequence, size, degree of structure formation , cationicity, hydrophobicity and amphipathicity. The analysis of numerous natural AMPs provided representative values for these parameters and led to a sequence template with which to generate potent artificial lead AMPs. Sequences were then varied in a rational manner, using both natural and nonproteinogenic amino acids, to probe the individual roles of each parameter in modulating biological activity . A high cationicity combined with a stabilized amphipathic α helical structure conferred enhanced cidal activity towards all the cell types considered, and was a requirement for Gram-positive bacteria and fungi. An elevated helicity also correlated with increased hemolytic activity. The structural requirements for activity against several Gram-negative bacteria were instead considerably less stringent, so that it persisted in peptides in which formation of a helical structure and/or amphipathicity were impeded. Either a reduced charge or a reduced hydrophobicity resulted in generally inactive peptides. These observations, combined with the kinetics of bacterial membrane permeabilization and time-killing are discussed in terms of currently accepted models of action for this type of peptide. The simple guidelines obtained in this study allowed the design of highly active shortened AMPs and may be generally useful in the development of this type of peptides as anti-infective agents.
