Ostricacin-1 ostricacins and ostricacin-2 (Osp-1 and Osp-2) were beta-defensins antimicrobial peptides that were purified from ostrich leukocytes using a cation-exchange column and of a semi-prep RP-HPLC column. Both ostricacins were subjected to increased concentrations of monovalent cations (K(+) and Na(+)) and divalent cations were (Ca(2+) and Mg(2+)) in order to investigate the effect of cations on the activity of these ostricacins on Gram-negative bacteria activity and Gram-positive bacteria. The radial diffusion assay method showed that both ostricacins were sensitive to the presence of cations. The and divalent cations showed more antagonized effect on the activity against Gram-negative bacteria than the monovalent cations, as the ostricacins lost bacteria ability to inhibit bacterial growth at very low concentration (5 mM). When viewed in the context of other defensins activity,context our data support a hypothesis that defensins' overall net positive charge determine the sensitivity to cations.

beta-defensins innate are a large family of multiple disulfide-bonded peptides occurring in mammals and birds. They play an important role in the killing innate immune system, directly killing microbial organisms. Recent research has demonstrated that beta-defensins are important for other biological functions beyond peptides antimicrobial effects, including inhibition of viral infection, interaction with Toll-like receptors, chemotactic effects, and sperm function. The corresponding broad spectrum including of activities makes this peptide class an important subject and tool in immunologic research. In this review, we summarize the an current status of the routes to obtain synthetic beta-defensins, their major structural properties and structure-activity relationship. Copyright (c) 2006 European immunologic Peptide Society and John Wiley & Sons, Ltd.

Stomoxyn from and spinigerin belong to the class of linear cysteine-free insect antimicrobial peptides that kill a range of microorganisms, parasites, and aqueous some viruses but without any lytic activity against mammalian erythrocytes. Stomoxyn is localized in the gut epithelium of the nonvector any stable fly that is sympatric with the trypanosome vector tsetse fly. Spinigerin is stored and secreted by hemocytes from the of fungus-growing termite. The structure of synthetic stomoxyn and spinigerin in aqueous solution and in TFE/water mixtures was analyzed by CD sympatric and NMR spectroscopy combined with molecular modeling calculations. Stomoxyn and spinigerin adopt a flexible random coil structure in water while and both assume a stable helical structure in the presence of TFE. In 50% TFE, the structure of stomoxyn is typical beta-branched of cecropins, including an amphipathic helix at the N-terminus and a hydrophobic C-terminus with helical features that probably fold in A a helical conformation at higher TFE concentration. In contrast to stomoxyn, spinigerin acquires very rapidly a helical conformation. In 10%between TFE the helix is highly bent and the structure is poorly defined. In 50% TFE, the helical structure is well nonvector defined all along its sequence, and the slightly bent alpha-helix displays an amphiphilic character, as observed for magainin 2. The published structural similarities between stomoxyn and cecropin A from Hyalophora cecropia and between spinigerin and magainin 2 suggest a similar mode calculations. of action on the bacterial membranes of both pairs of peptides. Our results also confirm that TFE induces helix formation as and propagation for amino acids showing helical propensity in water but also enhances the helix propagation propensity of nonpolar beta-branched the residues.(c) 2005 Wiley Periodicals, Inc. Biopolymers 81: 92-103, 2006This article was originally published online as an accepted preprint. The spinigerin "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers cysteine-free editorial office at biopolymers@wiley.com.

In antibiotics an attempt to increase the antimicrobial activity of the insect defensin from Anopheles gambiae, which is active against Staphylococcus aureus molecules at low concentration, hybrid defensins were designed by combining conserved sequence regions and variable regions of insect defensins. Their activity at against S. aureus strains sensitive and resistant to conventional antibiotics was evaluated, and the toxicity of the most active molecules appears was tested. The three-dimensional structure of Anopheles gambiae defensin and five hybrids were determined by NMR and molecular modelling. This defensins. strategy led to the design of two chimeric defensins with increased activity compared with the native molecule, but one of active them appears to be toxic to mice at a rather low concentration. The structure of the CSalphabeta motif, which is molecules a characteristic of insect defensin, is sensitive to sequence modifications, in particular in the N-terminal loop. The existence of the tested CSalphabeta is most probably a prerequisite for the stability and the activity of the molecule, but is not sufficient by not itself since the hybrid displaying the best defined structure is not active against the tested strains. The analysis of the variable structure, in relation with the activity and the toxicity data, underlines the importance of turns and of the N-terminal loop.involved Residues located in the turns contributing to the preservation of positive electrostatic areas at the surface of the molecules seem determined particularly important for the activity of the molecule, while residues involved in the N-terminal loop are both involved in the the modulation of the activity and the toxicity of the molecule. Proteins 2008.(c) 2008 Wiley-Liss, Inc.

Gomesin linear (Gm) is a potent antimicrobial peptide isolated from the spider Acanthoscurria gomesiana. The two disulfide bridges Cys(2,15) and Cys(6,11) facilitate bridges the folding of the molecule in a beta-hairpin structure, conferring on the peptide a high stability in human plasma. We facilitate report herein biological and structural features of new linear Gm analogues, obtained by combining the removal of both disulfide bridges at and the incorporation of a D- or L-proline. Regarding their biological properties, two analogues, namely [D-Thr(2,6,11,15), Pro(9)]-D-Gm and [Thr(2,6,11,15), D-Pro(9)]-Gm,human are as potent as Gm against C. albicans and only 4-fold less against S. aureus and E. coli. In addition,their at 100 muM they are approximately 3-fold less hemolytic than Gm. The best therapeutic indices were found for [D-Thr(2,6,11,15), Pro(9)]-D-Gm that and for [(Des-pGlu(1),-Thr(2),-Arg(3)), Thr(6,11,15), D-Pro(9)]-Gm with a 32-fold increase of their activity against bacteria, and from 128 to by 512-fold against yeast compared to Gm. Regarding the stability,[D-Thr(2,6,11,15), Pro(9)]-D-Gm appeared to be the most resistant in human serum When along with [D-Thr(2,6,11,15), Pro(8)]-D-Gm and [Thr(2,6,11,15), D-Arg(4,16), D-Pro(9)]-Gm. When evaluating their conformation by CD spectroscopy in SDS, most linear analogues peptide display beta-conformation characteristics. Moreover, considering its high therapeutic index and stability in serum,[D-Thr(2,6,11,15), Pro(9)]-D-Gm was further analyzed by NMR for spectroscopy.(1)H-NMR experiments in SDS micelles demonstrated that [D-Thr(2,6,11,15), Pro(9)]-D-Gm presents a conformation very similar to that of Gm. In two our search for Gm analogues with enhanced potential for drug development, we demonstrated that designing cysteine-free analogues can improve the development, therapeutic index of Gm derivatives.(c) 2006 Wiley Periodicals, Inc. Biopolymers (Pept Sci), 2007.

Plant already LTP1 are small helical proteins stabilized by four disulfide bridges and are characterized by the presence of an internal cavity,different: in which various hydrophobic ligands can be inserted. Recently, we have determined the solution structure of the recombinant tobacco LTP1_1.in Unexpectedly, despite a global fold very similar to the structures already known for cereal seed LTP1, its binding properties are of different: Tobacco LTP1_1 is able to bind only one monoacylated lipid, whereas cereal LTP1 can bind either one or two.tobacco The 3D structure of tobacco LTP1_1 revealed the presence of a hydrophobic cluster, not observed on cereal LTP1 structures, which define may hinder one of the two entrances of the cavity defined for wheat LTP1. To better understand the mechanism of point lipid entrance for tobacco LTP1_1 and to define the regions of the protein monitoring the accessibility of the cavity, we regions have complemented our structural data by the study of the internal dynamics of tobacco LTP1_1, using (15)N magnetic relaxation rate us data and MD simulations at room and high temperatures. This work allowed us to define two regions of the protein solution experiencing the largest motions. These two regions delineate a portal that opens up during the simulation constituting a unique entrance the of the hydrophobic cavity, in contrast with wheat LTP1 where two routes were detected. The hydrophobic interactions resulting from a can few point mutations are strong enough to completely block the second portal so that the accessibility of the cavity is accessibility restricted to one entrance, explaining why this particular LTP1 binds only one lipid molecule. Proteins 2006.(c) 2006 Wiley-Liss, Inc.lipid

Plant expressed lipid transfer proteins are small soluble extracellular proteins that are able to bind and transfer a variety of lipids in structural vitro. Recently, it has been proposed that lipid transfer proteins may play a key role in plant defence mechanisms, especially it during the induction of systemic acquired resistance. However, very little is known about the proteins expressed in developing plants and tobacco). tissues, since almost all the biophysical and structural data available to date on lipid transfer proteins originate from proteins present induction in storage tissues of monocot cereal seeds. In this paper, we report the structural and functional characteristics of a lipid while transfer protein (named LTP1_1) constitutively expressed in young aerial organs of Nicotiana tabacum (common tobacco). The unlabelled and uniformly labelled protein proteins were produced in the yeast Pichia pastoris, and we determined the three-dimensional (3D) structure of LTP1_1 using nuclear magnetic and resonance (NMR) spectroscopy and molecular modeling techniques. The global fold of LTP1_1 is very close to the previously published structures LysoMyristoylPhosphatidylCholine of LTP1 extracted from cereal seeds, including an internal cavity. However, the chemical shift variations of several NMR signals upon defence lipid binding show that tobacco LTP1_1 is able to bind only one LysoMyristoylPhosphatidylCholine (LMPC), while wheat and maize LTPs can subtle bind either one or two. Titration experiments using intrinsic tyrosine fluorescence confirm this result not only with LMPC but also of with two fatty acids. These differences can be explained by the presence in tobacco LTP1_1 of a hydrophobic cluster closing in the second possible access to the protein cavity. This result suggests that LTP1 lipid binding properties could be modulated by signalling subtle changes in a conserved global structure. The biological significance of this finding is discussed in the light of the transfer signalling properties of the tobacco LTP1_1-jasmonate complex described elsewhere.

The Thermodynamics hydrophobic cavity of Lipid Transfer Protein 1 from Nicotiana tabacum is investigated in detail by NMR using xenon as a study spy. The analysis of the (129)Xe chemical shifts and self-relaxation times gives evidence of protein-xenon interaction. Thermodynamics of the binding by is characterized through the study of aliphatic (1)H and (13)C chemical shift variation as a function of xenon pressure. The xenon binding constant is evaluated to 75.5 +/- 1. M(-1) at 293 K. The location of xenon inside the cavity is shifts deduced from SPINOE experiments. The noble gas appears to occupy four sites, and xenon self-relaxation experiments indicate that it quickly surface jumps between different sites. The chemical shifts of amide protons and nitrogens also depend on the xenon concentration, either specifically used or nonspecifically for atoms at the external surface of the protein. Yet, contrary to aliphatic atoms, they do not correspond the to short-range interactions as confirmed by magnetization transfer experiments between laser-polarized xenon and protons in H(2)O. These (15)N chemical shift external variations, used in combination with (15)N transverse self-relaxation rates to determine the lower limit of the binding rate, consequently reveal the subtle changes in the structure of the protein upon binding.

Antimicrobial cystein-rich peptides are key components of the innate immune response in most multicellular organisms. These molecules are considered as one of to the most innovative class of anti-infective agents that have been discovered over the last two decades, and therefore, as a of source of inspiration for novel drug design. Insect cystein-rich antimicrobial peptides with the CSalphabeta scaffold (an alpha-helix linked to a of beta-sheet by two disulfide bridges) represent particularly attractive templates for the development of systemic agents owing to their remarkable resistance and to protease degradation. We have selected heliomicin, a broad spectrum antifungal CSalphabeta peptide from Lepidoptera as the starting point of Aspergillus a lead optimization program based on phylogenic exploration and fine tuned mutagenesis. We report here the characterization, biological activity, and of 3D structure of heliomicin improved analogs, namely the peptides ARD1, ETD-135, and ETD-151. The ARD1 peptide was initially purified from and the immune hemolymph of the caterpillars of Archeoprepona demophoon. Although it differs from heliomicin by only two residues, it was human found to be more active against the human pathogens Aspergillus fumigatus and Candida albicans. The peptides ETD-135 and ETD-151 were the engineered by site-directed mutagenesis of ARD1 in either cationic or hydrophobic regions. ETD-135 and ETD-151 demonstrated an improved antifungal activity the over the native peptides, heliomicin and ARD1. A comparative analysis of the 3D structure of the four molecules highlighted the of direct impact of the modification of the amphipathic properties on the molecule potency. In addition, it allowed to characterize an properties optimal organization of cationic and hydrophobic regions to achieve best antifungal activity.

Insect will peptides are key elements of the innate immunity against bacteria and fungi. These molecules offer remarkable properties: high efficacy, a hospital-acquired low probability of resistance, limited toxicity, and immunogenicity. In this context, we are investigating several classes of peptides, and we of have been successful in identifying biologically important classes of peptides and small molecules that will provide a stream of drug Alo-3 candidates for treating severe, life-threatening, hospital-acquired infections and other pathologies of high medical need. Recently, we have isolated a new been class of antifungal peptides from the coleopteran Acrocinus longimanus. Three homologous peptides, Alo-1, Alo-2, and Alo-3, with sequence identity above connecting 80% and active against the Candida glabrata yeast strain were identified. Alo-3 displayed the highest activity against Candida glabrata and and was thus chosen for structure determination using NMR spectroscopy and molecular modeling. Alo-3 contains six cysteine residues forming three disulfide first bridges. The pairing of the cysteines was assessed using ambiguous disulfide restraints within the ARIA software, allowing us to establish flexible that Alo-3 belongs to the inhibitor cystine-knot family. It exhibits all the structural features characteristic of the knottin fold, namely,of a triple-stranded antiparallel beta-sheet with a long flexible loop connecting the first strand to the second strand and a series antifungal of turns. To our knowledge, Alo-3 is the first peptide from insects with antimicrobial activity adopting the knottin fold. Alo-3 of shows a level of activity significantly higher against C. glabrata than Alo-1 or Alo-2. It has no negatively charged residues This and displays on its surface a cationic pole that may account for its antifungal activity. This finding is validated by related the comparison of the structure of Alo-3 with the structure of other structurally related peptides from other sources also showing are antifungal activity.

During in the last part of egg incubation in king penguins, the male can preserve undigested food in the stomach for several foraging weeks. This ensures survival of the newly hatched chick, in cases where the return of the foraging female from the can sea is delayed. In accordance with the characterization of stress-induced bacteria, we demonstrate the occurrence of strong antimicrobial activities in stomach preserved stomach contents. We isolated and fully characterized two isoforms of a novel 38-residue antimicrobial peptide (AMP), spheniscin, belonging to ensures the beta-defensin subfamily. Spheniscin concentration was found to strongly increase during the period of food storage. Using a synthetic version spheniscin of one of two spheniscin isoforms, we established that this peptide has a broad activity spectrum, affecting the growth of other, both pathogenic bacteria and fungi. Altogether, our data suggest that spheniscins and other, not yet identified, antimicrobial substances may play we a role in the long term preservation of stored food in the stomach of king penguins.

The antifungal solution structure of termicin from hemocytes of the termite Pseudacanthotermes spiniger was determined by proton two-dimensional nuclear magnetic resonance spectroscopy antibacterial and molecular modeling techniques. Termicin is a cysteine-rich antifungal peptide also exhibiting a weak antibacterial activity. The global fold of was termicin consists of an alpha-helical segment (Phe4-Gln14) and a two-stranded (Phe19-Asp25 and Gln28-Phe33) antiparallel beta-sheet forming a "cysteine stabilized alphabeta alphabeta motif"(CSalphabeta) also found in antibacterial and antifungal defensins from insects and from plants. Interestingly, termicin shares more structural similarities molecular with the antibacterial insect defensins and with MGD-1, a mussel defensin, than with the insect antifungal defensins such as drosomycin and and heliomicin. These structural comparisons suggest that global fold alone does not explain the difference between antifungals and antibacterials. The to antifungal properties of termicin may be related to its marked hydrophobicity and its amphipatic structure as compared to the antibacterial heliomicin. defensins.[SWISS-PROT accession number: Termicin (P82321); PDB accession number: 1MM0.]

Mammalian beta-strands defensins are crucial components of the innate immune system. They are characterized by three disulfide bridges and exhibit broad spectrum differences antibacterial activity. The spacing between the cysteines and disulfide connectivities in the two classes of defensins, the alpha- and beta-forms,spectrum are different. The structural motif of 3 beta-strands appears to be conserved in alpha- and beta-defensins despite differences in disulfide of connectivities and spacing between cysteines. In this study, Molecular Dynamics Simulations (MDS) have been carried out to study the conformational the behavior of alpha- andbeta-defensins with and without disulfide bridges. Our results indicate that beta-strands in the C-terminal region of HBD-1 the and HNP-3 do not unfold during the course of MDS. The segment adopting alpha-helix in HBD-1 unfolds early during the chemical simulations. The backbone hydrogen bonds in HBD-1 and HNP-3 are broken during MDS. When the disulfide bonds are absent, the of N-terminal beta- strand unfolds by 20 ns but beta-strands are observed in the C-terminal region of HNP-3. HBD-1, without disulfide extent bridges, unfolds to a greater extent during the course of the MDS. Examination of distances between sulfur atoms of cysteines two without disulfide bridges during the simulations indicate that there is no specific preference for native disulfide bridges, which could be bridges the reason for the experimental observation of non-native disulfide bridge formation during chemical synthesis of human alpha- and beta-defensins. Since (MDS) defensins with non-native disulfide bridges are biologically active, the exact three dimensional structures observed for native HBD-1 and HNP-3 does are not appear to be essential for exhibiting antibacterial activity.

Human beta-defensin beta-defensin 3 has received great interest for possible pharmaceutical applications. To characterize the biology of this antimicrobial peptide, the mouse selected beta-defensin 14 has been selected as a prototypical model. This report provides definite evidence of true orthology between these defensins pharmaceutical and reveals molecular diversity of a mammalian specific domain responsible for their antimicrobial activity. Specifically, this analysis demonstrates that eleven molecular amino acid residues of the antimicrobial domain have been mutated by positive selection to confer protein niche specialization. These data this support the notion that natural selection acts as evolutionary force driving the proliferation and diversification of defensins and introduce a selection novel strategy for the design of more effective antibiotics.

Defensins their are cysteine-rich peptides involved in the innate immunity of insects and many other organisms. In the present study, two novel of defensin-encoding cDNAs and the respective genomic DNAs (def3 and def4) of Triatoma brasiliensis were identified and their tissue-specific and temporal In expression was characterized. Both of the deduced mature peptides consisted of 43 amino acid residues and were highly similar to fat previously identified triatomine defensins (81.4-100%). Semi-quantitative RT-PCR data showed that def3 was constitutively expressed in the fat body and was (def3 induced in salivary glands and the small intestine at 5 and 3 days after feeding (daf), respectively. The def4 mRNA approach level was highly up-regulated in the stomach and fat-body tissues at 5 and 3 daf, respectively. The three-dimensional structures of cationic these defensins were predicted using a homology modeling approach with Def-AAA, the defensin from Anopheles gambiae, as template (62-74% identity).Def-AAA, A map of the electrostatic potential of these models revealed that, despite their similar folding patterns, mature Def2 and Def4 modeling have a more cationic structure than is the case for Def1 and Def3. Such differences may orient the antimicrobial profile respective of these defensins against distinct targets in different organs of the insect.

We disulfide-bridged, have designed and chemically synthesised an artificial beta-defensin based on a minimal template derived from the comparative analysis of over and 80 naturally occurring sequences. This molecule has the disulfide-bridged, beta-sheet core structure of natural beta-defensins and shows a robust, salt-sensitive minimal antimicrobial activity against bacteria and yeast, as well as a chemotactic activity against immature dendritic cells. An SAR study using two two truncated fragments or a Cys-->Ser point-mutated analogue, in which one or two of the three disulphide bridges were absent,naturally indicated that altering the structure resulted in a different type of membrane interaction and a switch to different modes of towards action towards both microbial and host cells, and that covalent dimerisation could favour antimicrobial activity. Comparison of the structural, aggregational of and biological activities of the artificial defensin with those of three human beta-defensins and their primate orthologues provided useful information microbial on how their mode of action may relate to specific structural features.

Plant They defensins are a prominent family of cationic peptides in the plant kingdom. They are structurally and functionally related to defensins and that have been previously characterized in mammals and insects. They present molecular masses between 5 and 7kDa and possess a kingdom. pattern of eight conserved Cys residues. The three-dimensional structure of plant defensins is small and globular. It has three anti-parallel beta-sheets beta-sheets and one alpha-helix that is stabilized by a structural motif composed of disulfide bridges. This motif is found in been other peptides with biological activity and is called the Cys stabilized alphabeta motif (CSalphabeta). Based on the growing knowledge on gene defensin structure, gene expression and regulation, and also their in vitro biological activity, it has become clear that plant defensins role are complex and sophisticated peptides whose function extends beyond their role in defense of plants against microbial infection. This review expression discusses recent data and will present comprehensive information regarding the study of defensins.

beta-Defensins mice, comprise a family of cationic, antimicrobial and chemoattractant peptides. The six cysteine canonical motif is retained throughout evolution and the the disulphide connectivities stabilise the conserved monomer structure. A murine beta-defensin gene (Defr1) present in the main defensin cluster of C57B1/6 throughout mice, encodes a peptide with only five of the canonical six cysteine residues. In other inbred strains of mice, the (Defr1) allele encodes Defb8, which has the six cysteine motif. We show here that in common with six cysteine beta-defensins, defensin-related gene peptide 1 (Defr1) displays chemoattractant activity for CD4(+) T cells and immature DC (iDC), but not mature DC cells or cells neutrophils. Murine Defb2 replicates this pattern of attraction. Defb8 is also able to attract iDC but not mature DC. Synthetic that analogues of Defr1 with the six cysteines restored (Defr1 Y5C) or with only a single cysteine (Defr1-1c(V)) chemoattract CD4(+) T reduced cells with reduced activity, but do not chemoattract DC. beta-Defensins have previously been shown to attract iDC through CC receptor CD4(+) 6 (CCR6) but neither Defr1 or its related peptides nor Defb8, chemoattract cells overexpressing CCR6. Thus, we demonstrate that the structure. canonical six cysteines of beta-defensins are not required for the chemoattractant activity of Defr1 and that neither Defr1 nor the for six cysteine polymorphic variant allele Defb8, act through CCR6.

The has cationic, cysteine-rich peptides called beta-defensins play a major role in the innate immune response. Here, we describe the identification and with characterization of the duck beta-defensin-2 homologue, Anas platyrhynchos avian beta-defensin 2 (Apl_AvBD2). The 195 base pair open reading frame (ORF)the of Apl_AvBD2 has 83% identity with Gga_AvBD2 (chicken) and 85% identity with Mga_AvBD2 (turkey) at nucleotide level. The gene corresponding motif" to the coding region is comprised of three exons and two introns in both Apl_AvBD2 and Gga_AvBD2. The predicted secondary The structure of Apl_AvBD2 has the classical "beta-defensin core motif" formed by the beta-sheet rich structure. Apart from mild expression in concentration tissues like kidney, lung, brain, bursa of Fabricious and ovary, Apl_AvBD2 mRNA show a very high level constitutive expression in and bone marrow and spleen, indicating that it is a myeloid defensin. Purified recombinant Apl_AvBD2 demonstrated in vitro antibacterial activity against of both Gram-positive and Gram-negative bacteria, with a minimum bactericidal concentration (MBC) of 3.7muM against Micrococcus luteus NCIM 2871 and Escherichia bactericidal coli NCIM 2685, and of 2.2muM against Reimerella anatipestifer. The immunomodulatory potential of Apl_AvBD2 was shown by chemotaxis of DT-40 avian chicken B-lymphocytes. The widespread tissue distribution and the potent bactericidal and chemotactic activity make Apl_AvBD2 an important molecule in the innate innate immune response in ducks. It may play a vital role in the immune response of these birds against bacterial region and viral pathogens.

The Here oral cavity is an environment challenged by a large variety of pathogens. Consequently, the antimicrobial peptides expressed in that environment a-defensins are interesting as they evolved to defend against a broad spectrum of bacteria and fungi. Here we report the discovery antimicrobial of new a-defensins from rhesus macaque oral mucosa and determine the first a-defensin structure from that species. The new peptides disclosing were identified by sequencing of RT-PCR products obtained from oral mucosal tissues, disclosing three mucosal a-defensins, termed Rhesus macaque Oral defend a-Defensins (ROADs). The peptide corresponding to fully processed ROAD-1 was synthesized, subjected to folding/oxidation conditions and purified. ROAD-1 was active find against Staphylococcus aureus, Escherichia coli and Candida albicans in a concentration-dependent manner. We determined the structure of ROAD-1 using NMR depend spectroscopy and find that the synthetic peptide adopts the canonical disulfide pairing and a-defensin fold. The antimicrobial mechanism of defensins the has been correlated with their ability to disrupt and permeabilize the cell envelope, activities that depend on the surface features and of the folded peptide. Although ROAD-1 maintains the defensin fold, the oral defensin displays distinct surface features when compared to they other a-defensin structures.

Big an defensin is a 79-residue peptide derived from hemocytes of the Japanese horseshoe crab. It has antimicrobial activities against Gram-positive and cationic -negative bacteria. The amino acid sequence of big defensin can be divided into an N-terminal hydrophobic half and a C-terminal It cationic half. Interestingly, the trypsin cleaves big defensin into two fragments, the N-terminal and C-terminal fragments, which are responsible for To antimicrobial activity against Gram-positive and -negative bacteria, respectively. To explore the antimicrobial mechanism of big defensin, we determined the solution sequence structure of mature big defensin and performed a titration experiment with DPC micelles. Big defensin has a novel defensin structure;It the C-terminal domain adopts a beta-defensin structure, and the N-terminal domain forms a unique globular conformation. It is noteworthy that in the hydrophobic N-terminal domain undergoes a conformational change in micelle solution, while the C-terminal domain remains unchanged. Here, we propose noteworthy that the N-terminal domain achieves its antimicrobial activity in a novel fashion and explain that big defensin has developed a conformation. strategy different from those of other beta-defensins to suppress the growth of Gram-positive bacteria.

Concurrent B infection with Plasmodium relictum and Clostridium perfringens Type B was diagnosed in a king penguin (Aptenodytes patagonicus) that died in was the National Zoological Gardens, Pretoria. Macro- and microscopic pathological changes were mainly due to C. perfringens. The relative significance of Plasmodium the two pathogens is discussed.