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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A humoral immune response in larvae of the coleopteran insect, Anomala cuprea has been examined for exploring the molecular basis of host-pathogen interactions. The antibacterial activity against the Gram-positive strain, Micrococcus luteus was detected at a low level in absence of injection. The activity increased strikingly in the hemolymph of the larvae challenged with Escherichia coli, showing the fluctuating profile through a time course, which consists of the static induction phase, the production phase rising to a maximum level, and the reduction phase extending over a long duration. Two peptides were purified and characterized by reverse-phase HPLC, Edman degradation and mass spectrometry. They were isoforms, composed of similar sequences with two amino acid substitutions in 43 residues, and novel members of the insect defensins, cysteine-rich antibacterial peptides. Anomala defensins A and B showed potent activity against Gram-positive bacteria, with slight differences in activity against a few strains of tested bacteria. Anomala defensin B was active at high concentration of 40 microM against the Gram-negative strain, Xenorhabdus japonicus, a pathogen toward the host, A. cuprea larvae.
Insect Biochem Mol Biol 2001 Dec
PMID:Two novel insect defensins from larvae of the cupreous chafer, Anomala cuprea: purification, amino acid sequences and antibacterial activity. 1171 71

Pisum sativum defensin 1 (Psd1) is a 46 amino acid residue plant defensin isolated from seeds of pea. The three-dimensional structure in solution of Psd1 was determined by two-dimensional NMR data recorded at 600 MHz. Experimental restraints were used for structure calculation using CNS and torsion-angle molecular dynamics. The 20 lowest energy structures were selected and further subjected to minimization, giving a root-mean-square deviation of 0.78(+/- 0.22) A in the backbone and 1.91(+/-0.60) A for over all atoms of the molecule. The protein has a globular fold with a triple-stranded antiparalell beta-sheet and an alpha-helix (from residue Asn17 to Leu27). Psd1 presents the so called "cysteine stabilized alpha/beta motif" and presents identical three-dimensional topology in the backbone with other defensins and neurotoxins. Comparison of the electrostatic surface potential among proteins with high three-dimensional (selected using the softwares TOP and DALI) topology gave insights into the mode of action of Psd1. The surface topologies between proteins that present antifungal activity or sodium channel inhibiting activity are different. On the other hand the surface topology presents several common features with potassium channel inhibitors, suggesting that Psd1 presents this activity. Other common features with potassium channel inhibitors were found including the presence of a lysine residue essential for inhibitory activity. The identity of Psd1 in primary sequence is not enough to infer a mechanism of action, in contrast with the strategy proposed here.
J Mol Biol 2002 Jan 25
PMID:Solution structure of Pisum sativum defensin 1 by high resolution NMR: plant defensins, identical backbone with different mechanisms of action. 1181 44

Several dipteran insects are vectors of parasites causing major human infectious diseases. Among these, the tsetse fly, Glossina spp., is responsible for the transmission of trypanosomes, the pathogens responsible for sleeping sickness in Africa. A better understanding of insect-parasite interactions will help establish new strategies to fight this important often fatal disease. Antimicrobial peptides (AMPs) are part of the humoral immune response in insects during bacterial, fungal and parasitic infections. Here, we studied the immune response of Glossina morsitans to bacteria and to Trypanosoma brucei brucei by analyzing the synthesis of AMPs as markers of the humoral immune response. By reversed-phase chromatography, mass spectrometry analysis, Edman degradation and in vitro antimicrobial assays of the hemolymph of immune-challenged adults of G. morsitans, we identified three AMPs: a cecropin, an attacin and a defensin. These three AMPs were found to be induced upon systemic bacterial infection and also after per os infections by bacteria and parasites.
Insect Biochem Mol Biol 2002 Apr
PMID:Immunopeptides in the defense reactions of Glossina morsitans to bacterial and Trypanosoma brucei brucei infections. 1188 71

The Stomoxys midgut defensin (Smd) family of genes are exclusively expressed in the anterior midgut of adult flies. Their putative function is protection of the stored bloodmeal from microbial attack. Smd genes are constitutively expressed, up-regulated in response to a bloodmeal and further up-regulated by immune stimulation per os but only in the presence of a bloodmeal not a sugar meal. Smd genes are down-regulated in response to a systemic immune challenge. Smd gene constructs transfected into l(2)mbn cells undertake constitutive expression but are not up-regulated by immune challenge. Electrophoretic mobility shift assays (EMSA) suggest the rel-like sites in the proximal promoter region of Smd genes do not bind midgut factors and so are non-functional.
Insect Mol Biol 2001 Dec
PMID:Regulation of midgut defensin production in the blood-sucking insect Stomoxys calcitrans. 1190 25

Using ELISA we provide direct evidence that the midgut defensins of the blood-sucking fly Stomoxys calcitrans are secreted into the gut lumen. We show that midgut defensin peptide levels increase up to fortyfold in response to a blood meal but not to a sugar meal. The data suggests the midgut defensin genes are post-transcriptionally regulated and that their function is protection of the stored blood meal from bacterial attack while it awaits digestion. Using recombinant defensins produced in Pichia pastoris we demonstrate that while in the gut cells the midgut defensins are bound in an SDS-stable complex to proteins with an apparent molecular weight of > 26 kDa from which they are released when secreted into the gut lumen. This > 26 kDa protein (Ssp3) has been cloned and sequenced and is a member of the serine protease S1 family with homologies to multiple insect proteases and to vertebrate trypsins and elastases.
Insect Mol Biol 2002 Jun
PMID:Association of midgut defensin with a novel serine protease in the blood-sucking fly Stomoxys calcitrans. 1200 Jun 38

Antimicrobial peptides are expressed in the skin of amphibians and are used to prevent infection by microorganisms. Frog species store distinct collections of antimicrobial peptides that show variation in size, charge, conformation, and bactericidal activity, and so the evolution of antimicrobial peptide gene families may reflect the adaptive diversification of these loci. We examined the molecular evolution of antimicrobial peptide transcripts from hylid and ranid frog species. Our results show that after the gene family arose in the common ancestor of the Hylidae and Ranidae, before the divergence of these families in the Mesozoic, it subsequently diversified within these groups with numerous duplication events and divergence of loci. Moreover, we provide evidence that suggests that members of the antimicrobial peptide gene family have been subject to diversifying selection within both propiece and mature domains of hylids and solely within the mature domain of ranids. Finally, our results suggest that coordinated and compensatory amino acid replacements have occurred within the acidic propiece and cationic mature domain of hylid antimicrobial peptide precursors, as has been observed for mammalian defensin genes, but not among those of ranid precursors.
Mol Biol Evol 2002 Jun
PMID:Roles of diversifying selection and coordinated evolution in the evolution of amphibian antimicrobial peptides. 1203 42

We isolated a stamen-specific cDNA, BSD1 (Brassica stamen specific plant defensin 1) that encodes a novel plant defensin peptide in Chinese cabbage (Brassica campestris L. ssp. pekinensis). Plant defensins are antimicrobial peptides containing eight highly conserved cysteine residues linked by disulfide bridges. In BSD1, the eight cysteine residues and a glutamate residue at position 29 are conserved whereas other amino acid residues of the plant defensins consensus sequence are substituted. BSD1 transcripts accumulate specifically in the stamen of developing flowers and its level drops as the flowers mature. The recombinant BSD1 produced in Escherichia coli showed antifungal activity against several phytopathogenic fungi. Furthermore, constitutive over-expression of the BSD1 gene under the control of the cauliflower mosaic virus (CaMV) 35S promoter conferred enhanced tolerance against the Phytophthora parasitica in the transgenic tobacco plants.
Plant Mol Biol 2002 Sep
PMID:Characterization of a stamen-specific cDNA encoding a novel plant defensin in Chinese cabbage. 1213 9

Elucidation of molecular mechanisms underlying stage- and tissue-specific expression of genes activated by a blood meal is of great importance for current efforts directed towards utilizing molecular genetics to develop novel strategies of mosquito and pathogen control. Regulatory regions of such genes can be used to express anti-pathogen effector molecules in engineered vectors in a precise temporal and spatial manner, designed to maximally affect a pathogen. The fat body is a particularly important target for engineering anti-pathogen properties because in insects, it is a potent secretory tissue releasing its products to the hemolymph, an environment or a crossroad for most pathogens. Recently, we have provided proof of this concept by engineering stable transformant lines of Aedes aegypti mosquito, in which the regulatory region A. aegypti vitellogenin (Vg) gene activates high-level fat body-specific expression of a potent anti-bacterial factor, defensin, in response to a blood meal. Further study of the Vg gene utilizing Drosophila and Aedes transformation identified cis-regulatory sites responsible for state- and fat body-specific activation of this gene via a blood-meal-triggered cascade. These analyses revealed three regulatory regions in the 2.1-kb upstream portion of the Vg gene. The proximal region, containing binding sites to EcR/USP, GATA, C/EBP and HNF3/fkh, is required for the correct tissue- and stage-specific expression at a low level. The median region, carrying sites for early ecdysone response factors E74 and E75, is responsible for a stage-specific hormonal enhancement of the Vg expression. Finally, the distal GATA-rich region is necessary for extremely high expression levels characteristic to the Vg gene. Furthermore, our study showed that several transcription factors involved in controlling the Vg gene expression, are themselves targets of the blood meal-mediated regulatory cascade, thus greatly amplifying the effect of this cascade on the Vg gene. This research serves as the foundation for the future design of mosquito-specific expression cassettes with predicted stage- and tissue specificity at the desired levels of transgene expression.
Insect Biochem Mol Biol 2002 Oct
PMID:Molecular biology of mosquito vitellogenesis: from basic studies to genetic engineering of antipathogen immunity. 1222 18

Two defensin genes A and B were previously demonstrated to be up-regulated by blood feeding in the soft tick, Ornithodoros moubata [Nakajima et al. (2001) Two isoforms of a member of the arthropod defensin family from the soft tick, Ornithodoros moubata (Acari: Argasidae). Insect Biochem Mol Biol 31: 747-751]. In this study, two defensin isoforms C and D similar to defensins A and B were newly cloned. A total of four defensins have been identified in O. moubata. All four Ornithodoros defensins are coded as prepro-defensins. Ornithodoros defensin genes consist of four exons and three introns, an organization reported in mussel defensins but not insect defensins. Ornithodoros defensin C and D genes are predominantly expressed in the midgut and up-regulated in response to blood feeding. The mature peptide of the previously cloned Ornithodoros defensin A was purified from the midgut lumen, indicating defensin is secreted into the midgut. These findings confirm the involvement of Ornithodoros defensin in midgut immunity.
Insect Mol Biol 2002 Dec
PMID:Antibacterial peptide defensin is involved in midgut immunity of the soft tick, Ornithodoros moubata. 1242 19

NMR spectroscopy and simulated annealing calculations have been used to determine the three-dimensional structure of NaD1, a novel antifungal and insecticidal protein isolated from the flowers of Nicotiana alata. NaD1 is a basic, cysteine-rich protein of 47 residues and is the first example of a plant defensin from flowers to be characterized structurally. Its three-dimensional structure consists of an alpha-helix and a triple-stranded antiparallel beta-sheet that are stabilized by four intramolecular disulfide bonds. NaD1 features all the characteristics of the cysteine-stabilized alphabeta motif that has been described for a variety of proteins of differing functions ranging from antibacterial insect defensins and ion channel-perturbing scorpion toxins to an elicitor of the sweet taste response. The protein is biologically active against insect pests, which makes it a potential candidate for use in crop protection. NaD1 shares 31% sequence identity with alfAFP, an antifungal protein from alfalfa that confers resistance to a fungal pathogen in transgenic potatoes. The structure of NaD1 was used to obtain a homology model of alfAFP, since NaD1 has the highest level of sequence identity with alfAFP of any structurally characterized antifungal defensin. The structures of NaD1 and alfAFP were used in conjunction with structure-activity data for the radish defensin Rs-AFP2 to provide an insight into structure-function relationships. In particular, a putative effector site was identified in the structure of NaD1 and in the corresponding homology model of alfAFP.
J Mol Biol 2003 Jan 03
PMID:The three-dimensional solution structure of NaD1, a new floral defensin from Nicotiana alata and its application to a homology model of the crop defense protein alfAFP. 1247 60


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