| 21829689 |
SUMOylation of DEC1 protein regulates its transcriptional activity and enhances its stability |
10.1371/journal.pone.0023046. |
PLoS One |
SUMOylation of DEC1 protein regulates its transcriptional activity and enhances its stability
Abstract
- Differentiated embryo-chondrocyte expressed gene 1 (DEC1, also known as sharp2, stra13, or BHLHB2) is a mammalian basic helix-loop-helix protein that is involved in many aspects of gene regulation through acting as a transcription factor. Changes in DEC1 expression levels have been implicated in the development of cancers. Using COS-7 cell, we showed that DEC1 can be modified by the small ubiquitin-like modifiers, SUMO1, 2 and 3. Two major SUMOylation sites (K(159) and K(279)) were identified in the C-terminal domain of DEC1. Substitution of either K(159) or K(279) with arginine reduced DEC1 SUMOylation, but substitution of both K(159) and K(279) abolished SUMOylation, and more protein appeared to be retained in the cytoplasm compared to wild-type DEC1. The expression of DEC1 was up-regulated after serum starvation as previously reported, but at the same time, serum starvation also led to more SUMOylation of DEC1. In MCF-7 cells SUMOylation also stabilized DEC1 through inhibiting its ubiquitination. Moreover, SUMOylation of DEC1 promoted its repression of CLOCK/BMAL1-mediated transcriptional activity through recruitment of histone deacetylase1. These findings suggested that posttranslational modification of DEC1 in the form of SUMOylation may serve as a key factor that regulates the function of DEC1 in vivo.
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| 21861545 |
Plerixafor: a review of its use in stem-cell mobilization in patients with lymphoma or multiple myeloma |
10.2165/11206040-000000000-00000. |
Drugs |
Plerixafor: a review of its use in stem-cell mobilization in patients with lymphoma or multiple myeloma
Abstract
- Plerixafor (Mozobil®) is a CXCR4 chemokine receptor antagonist that is indicated for use in combination with granulocyte colony-stimulating factor (G-CSF) to mobilize stem cells to the peripheral blood for collection and subsequent autologous stem-cell transplantation in patients who have non-Hodgkin's lymphoma (NHL) or multiple myeloma (MM) [US] and in patients who have lymphoma or MM and are poor mobilizers (EU). This article reviews the clinical efficacy and tolerability of subcutaneous plerixafor for stem-cell mobilization in patients with lymphoma or MM, as well as summarizing its pharmacological properties. Pharmacoeconomic analyses of plerixafor and decision-making algorithms intended to optimize its use are also discussed. Plerixafor plus G-CSF mobilized stem cells more efficiently than placebo plus G-CSF in adults with NHL or MM, according to the results of two randomized, double-blind, multicentre trials. In these trials, significantly more plerixafor plus G-CSF recipients than placebo plus G-CSF recipients reached primary apheresis targets in significantly fewer apheresis days. In the trial in patients with NHL, significantly more plerixafor plus G-CSF than placebo plus G-CSF recipients proceeded to transplantation. Results of compassionate-use studies in patients with lymphoma or MM demonstrated that plerixafor plus G-CSF successfully mobilized stem cells in the majority of patients who were poor mobilizers (i.e. sufficient CD34+ cells had not been collected during apheresis or apheresis had not occurred because of low peripheral blood CD34+ cell counts). Results of compassionate-use studies and additional studies in patients with lymphoma or MM also demonstrated that plerixafor plus G-CSF successfully mobilized stem cells in predicted poor mobilizers, such as heavily pretreated patients considered to be at high risk of mobilization failure. In addition, a small study showed mobilization with pre-emptive plerixafor to be effective. Subcutaneous plerixafor was generally well tolerated during stem-cell mobilization in patients with NHL or MM; the most commonly occurring treatment-related adverse events in plerixafor plus G-CSF recipients included injection-site reactions and gastrointestinal adverse events. Preliminary results of a US cost-effectiveness analysis suggest that plerixafor plus G-CSF is a cost-saving option compared with cyclophosphamide plus G-CSF. A retrospective US cost analysis found no significant difference between plerixafor plus G-CSF and cyclophosphamide plus G-CSF recipients in the median total cost of initial mobilization, suggesting that the cost of plerixafor may be offset by increased utilization of other resources in patients receiving alternative mobilization regimens. Additional cost analyses examined the use of pre-emptive plerixafor; institutions have developed decision-making algorithms, mainly relating to the use of pre-emptive plerixafor, to help optimize its use. In conclusion, plerixafor is a valuable stem-cell mobilizer for use in combination with G-CSF in patients with lymphoma or MM, particularly in patients who are poor mobilizers or predicted poor mobilizers.
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| 21867685 |
Characterization of novel antimicrobial peptides from the skin of the endangered frog Odorrana ishikawae by shotgun cDNA cloning |
10.1016/j.bbrc.2011.08.023. |
Biochem Biophys Res Commun |
Characterization of novel antimicrobial peptides from the skin of the endangered frog Odorrana ishikawae by shotgun cDNA cloning
Abstract
- We recently reported the primary structures, antimicrobial activities and cDNA precursors of nine novel antimicrobial peptides from the skin of the endangered anuran species, Odorranaishikawae. Their cDNA clones revealed a highly conserved approximately 60 bp region upstream of the start codon. This conserved region was used in the "shotgun" cDNA cloning method to reveal additional cDNAs encoding novel antimicrobial peptides of O.ishikawae. After sequencing 344 clones, we identified novel 13 cDNAs encoding dermal peptides in addition to the previously identified nine antimicrobial peptides. These 13 unique cDNAs encoded precursor proteins each containing a signal peptide, an N-terminal acidic spacer domain, a Lys-Arg/Lys processing site and a dermal peptide at the C-terminus. The dermal peptides were members of the palustrin-2 (two peptides; termed palustrin-2ISc and palustrin-2ISd), nigrocin-2 (one peptide; nigrocin-2ISc), brevinin-1 (one peptide; brevinin-1ISa), odorranain-M (one peptide; odorranain-MISa) and entirely novel peptides (eight peptides; ishikawain-1-8). Although palustrin-2ISd and odorranain-MISa had few antimicrobial activities, palustrin-2ISc and nigrocin-2ISc possessed a broad-spectrum of growth inhibition against bacteria. Brevinin-1ISa had the most potent antimicrobial activities against the Gram-positive bacteria and the fungus but not the Gram-negative bacterium, Escherichiacoli. However, eight novel peptides showed no growth inhibition against these microorganisms.
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| 21873420 |
Identification and characterization of a new family of cell-penetrating peptides: cyclic cell-penetrating peptides |
10.1074/jbc.M111.264424. |
J Biol Chem |
Identification and characterization of a new family of cell-penetrating peptides: cyclic cell-penetrating peptides
Abstract
- Cell-penetrating peptides can translocate across the plasma membrane of living cells and thus are potentially useful agents in drug delivery applications. Disulfide-rich cyclic peptides also have promise in drug design because of their exceptional stability, but to date only one cyclic peptide has been reported to penetrate cells, the Momordica cochinchinensis trypsin inhibitor II (MCoTI-II). MCoTI-II belongs to the cyclotide family of plant-derived cyclic peptides that are characterized by a cyclic cystine knot motif. Previous studies in fixed cells showed that MCoTI-II could penetrate cells but kalata B1, a prototypic cyclotide from a separate subfamily of cyclotides, was bound to the plasma membrane and did not translocate into cells. Here, we show by live cell imaging that both MCoTI-II and kalata B1 can enter cells. Kalata B1 has the same cyclic cystine knot structural motif as MCoTI-II but differs significantly in sequence, and the mechanism by which these two peptides enter cells also differs. MCoTI-II appears to enter via macropinocytosis, presumably mediated by interaction of positively charged residues with phosphoinositides in the cell membrane, whereas kalata B1 interacts directly with the membrane by targeting phosphatidylethanolamine phospholipids, probably leading to membrane bending and vesicle formation. We also show that another plant-derived cyclic peptide, SFTI-1, can penetrate cells. SFTI-1 includes just 14 amino acids and, with the exception of its cyclic backbone, is structurally very different from the cyclotides, which are twice the size. Intriguingly, SFTI-1 does not interact with any of the phospholipids tested, and its mechanism of penetration appears to be distinct from MCoTI-II and kalata B1. The ability of diverse disulfide-rich cyclic peptides to penetrate cells enhances their potential in drug design, and we propose a new classification for them, i.e. cyclic cell-penetrating peptides.
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| 21888371 |
NRPS substrate promiscuity diversifies the xenematides |
10.1021/ol2020237. |
Org Lett |
NRPS substrate promiscuity diversifies the xenematides
Abstract
- Xenematide, a cyclic depsipeptide antibiotic produced by Xenorhabdus nematophila, had a candidate nonribosomal peptide synthetase (NRPS) with atypical features. Differential metabolite analysis between a mutant and wildtype validated that this stand-alone NRPS was required for xenematide production, and further analysis led to a series of new xenematide derivatives encoded by the same NRPS. Our results indicate that adenylation domain promiscuity and relaxed downstream processing in the X. nematophila NRPS provide a conduit for xenematide diversification.
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| 21888386 |
Effects of cyclization on stability, structure, and activity of α-conotoxin RgIA at the α9α10 nicotinic acetylcholine receptor and GABA(B) receptor |
10.1021/jm201060r. |
J Med Chem |
Effects of cyclization on stability, structure, and activity of α-conotoxin RgIA at the α9α10 nicotinic acetylcholine receptor and GABA(B) receptor
Abstract
- α-Conotoxin RgIA is of interest as a lead in the development of drugs for neuropathic pain. It modulates the α9α10 nicotinic acetylcholine receptor (nAChR) and the GABA(B) receptor, both of which are implicated in antinociception. However, because of its peptidic nature, RgIA is potentially susceptible to generic problems encountered by peptide-based drugs of poor oral bioavailability, short biological half-life, and low stability. Here, we improved the biopharmaceutical properties of RgIA by backbone cyclization using 3-7 residue peptidic linkers. Cyclization with a six-residue linker does not perturb the overall structure of RgIA, improves selectivity for the GABA(B) receptor over the α9α10 nAChR, and improves stability in human serum. The results provide insights to further improve the therapeutic properties of RgIA and other conotoxins being considered as drug leads and confirm that cyclization is a readily applicable strategy to improve the stability of peptides with proximate N- and C-termini.
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| 21903231 |
Lagunamide C, a cytotoxic cyclodepsipeptide from the marine cyanobacterium Lyngbya majuscula |
10.1016/j.phytochem.2011.08.019. |
Phytochemistry |
Lagunamide C, a cytotoxic cyclodepsipeptide from the marine cyanobacterium Lyngbya majuscula
Abstract
- Lagunamide C (1) is a cytotoxic cyclodepsipeptide isolated from the marine cyanobacterium, Lyngbya majuscula, from the western lagoon of Pulau Hantu Besar, Singapore. The complete structural characterization of the molecule was achieved by extensive NMR spectroscopic analysis as well as chemical manipulations. Several methods, including the advanced Marfey's method, a modified method based on derivatization with Mosher's reagents and analysis using LC-MS, and the use of (3)J(H-H) coupling constant values, were utilized for the determination of its absolute configuration. Compound 1 is related to the aurilide-class of molecules and it differs mainly in the macrocyclic structure by having a 27 membered ring system due to additional methylene carbon in the polyketide moiety. Lagunamide C displayed potent cytotoxic activity against a panel of cancer cell lines, such as P388, A549, PC3, HCT8, and SK-OV3 cell lines, with IC(50) values ranging from 2.1 nM to 24.4 nM. Compound 1 also displayed significant antimalarial activity with IC(50) value of 0.29 μM when tested against Plasmodium falciparum. In addition, lagunamide C exhibited weak anti-swarming activity when tested at 100 ppm against the Gram-negative bacterial strain, Pseudomonas aeruginosa PA01.
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| 21903752 |
Lipidomics of Candida albicans biofilms reveals phase-dependent production of phospholipid molecular classes and role for lipid rafts in biofilm formation |
10.1099/mic.0.051086-0. |
Microbiology (Reading) |
Lipidomics of Candida albicans biofilms reveals phase-dependent production of phospholipid molecular classes and role for lipid rafts in biofilm formation
Abstract
- Candida albicans-associated bloodstream infections are linked to the ability of this yeast to form biofilms. In this study, we used lipidomics to compare the lipid profiles of C. albicans biofilms and planktonic cells, in early and mature developmental phases. Our results showed that significant differences exist in lipid composition in both developmental phases. Biofilms contained higher levels of phospholipid and sphingolipids than planktonic cells (nmol per g biomass, P<0.05 for all comparisons). In the early phase, levels of lipid in most classes were significantly higher in biofilms compared to planktonic cells (P≤0.05). The ratio of phosphatidylcholine to phosphatidylethanolamine was lower in biofilms compared to planktonic cells in both early (1.17 vs 2.52, P≤0.001) and late (2.34 vs 3.81, P≤0.001) developmental phases. The unsaturation index of phospholipids decreased with time, with this effect being particularly strong for biofilms. Inhibition of the biosynthetic pathway for sphingolipid [mannosyl diinositolphosphoryl ceramide, M(IP)₂C] by myriocin or aureobasidin A, and disruption of the gene encoding inositolphosphotransferase (Ipt1p), abrogated the ability of C. albicans to form biofilms. The differences in lipid profiles between biofilms and planktonic Candida cells may have important implications for the biology and antifungal resistance of biofilms.
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| 21906641 |
Cellular uptake of cyclotide MCoTI-I follows multiple endocytic pathways |
10.1016/j.jconrel.2011.08.030. |
J Control Release |
Cellular uptake of cyclotide MCoTI-I follows multiple endocytic pathways
Abstract
- Cyclotides are plant-derived proteins that naturally exhibit various biological activities and whose unique cyclic structure makes them remarkably stable and resistant to denaturation or degradation. These attributes, among others, make them ideally suited for use as drug development tools. This study investigated the cellular uptake of cyclotide, MCoTI-I in live HeLa cells. Using real time confocal fluorescence microscopy imaging, we show that MCoTI-I is readily internalized in live HeLa cells and that its endocytosis is temperature-dependent. Endocytosis of MCoTI-I in HeLa cells is achieved primarily through fluid-phase endocytosis, as evidenced by its significant colocalization with 10K-dextran, but also through other pathways as well, as evidenced by its colocalization with markers for cholesterol-dependent and clathrin-mediated endocytosis, cholera toxin B and EGF respectively. Uptake does not appear to occur only via macropinocytosis as inhibition of this pathway by Latrunculin B-induced disassembly of actin filaments did not affect MCoTI-I uptake and treatment with EIPA which also seemed to inhibit other pathways collectively inhibited approximately 80% of cellular uptake. As well, a significant amount of MCoTI-I accumulates in late endosomal and lysosomal compartments and MCoTI-I-containing vesicles continue to exhibit directed movements. These findings demonstrate internalization of MCoTI-I through multiple endocytic pathways that are dominant in the cell type investigated, suggesting that this cyclotide has ready access to general endosomal/lysosomal pathways but could readily be re-targeted to specific receptors through addition of targeting ligands.
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| 21911019 |
Identification and structure-activity relationship of an antimicrobial peptide of the palustrin-2 family isolated from the skin of the endangered frog Odorrana ishikawae |
10.1016/j.peptides.2011.08.024. |
Peptides |
Identification and structure-activity relationship of an antimicrobial peptide of the palustrin-2 family isolated from the skin of the endangered frog Odorrana ishikawae
Abstract
- Recently, we identified nine novel antimicrobial peptides from the skin of the endangered anuran species, Odorrana ishikawae, to assess its innate immune system. In this study an additional antimicrobial peptide was initially isolated based on antimicrobial activity against Escherichia coli. The new antimicrobial peptide belonging to the palustrin-2 family was named palustrin-2ISb. It consists of 36 amino acid residues including 7 amino acids C-terminal to the cyclic heptapeptide Rana box domain. The peptide's primary structure suggests a close relationship with the Chinese odorous frog, Odorrana grahami. The cloned cDNA encoding the precursor protein contained a signal peptide, an N-terminal acidic spacer domain, a Lys-Arg processing site and the C-terminal precursor antimicrobial peptide. It also contained 3 amino acid residues at the C-terminus not found in the mature peptide. Finally, the antimicrobial activities against four microorganisms (E. coli, Staphylococcus aureus, methicillin-resistant S. aureus and Candida albicans) were investigated using several synthetic peptides. A 29 amino acid truncated form of the peptide, lacking the 7 amino acids C-terminal to the Rana box, possessed greater antimicrobial activities than the native structure.
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| 21914818 |
A BEN-domain-containing protein associates with heterochromatin and represses transcription |
10.1242/jcs.086603. |
J Cell Sci |
A BEN-domain-containing protein associates with heterochromatin and represses transcription
Abstract
- In eukaryotes, higher order chromatin structure governs crucial cellular processes including DNA replication, transcription and post-transcriptional gene regulation. Specific chromatin-interacting proteins play vital roles in the maintenance of chromatin structure. We have identified BEND3, a quadruple BEN domain-containing protein that is highly conserved amongst vertebrates. BEND3 colocalizes with HP1 and H3 trimethylated at K9 at heterochromatic regions in mammalian cells. Using an in vivo gene locus, we have been able to demonstrate that BEND3 associates with the locus only when it is heterochromatic and dissociates upon activation of transcription. Furthermore, tethering BEND3 inhibits transcription from the locus, indicating that BEND3 is involved in transcriptional repression through its interaction with histone deacetylases and Sall4, a transcription repressor. We further demonstrate that BEND3 is SUMOylated and that such modifications are essential for its role in transcriptional repression. Finally, overexpression of BEND3 causes premature chromatin condensation and extensive heterochromatinization, resulting in cell cycle arrest. Taken together, our data demonstrate the role of a novel heterochromatin-associated protein in transcriptional repression.
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| 21918875 |
Synchrotron vacuum ultraviolet (VUV) photo-induced fragmentation of cyclic dipeptides radical cations |
10.1007/s00726-011-1072-2. |
Amino Acids |
Synchrotron vacuum ultraviolet (VUV) photo-induced fragmentation of cyclic dipeptides radical cations
Abstract
- Cyclic dipeptides, due to their chemical properties and various bioactivities, are very attractive for medicinal chemistry. Fragmentations of three simple cyclic dipeptides including cyclo(Gly-Gly), cyclo(Ala-Ala) and cyclo(Gly-Val) in the gas-phase are determined with synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (VUV PIMS) and theoretical calculations. Cyclo(Gly-Gly) and cyclo(Ala-Ala) show the similar fragmentation pathways. The primary decomposition reactions of cyclo(Gly-Gly) and cyclo(Ala-Ala) radical cations are found to be HNCO loss and CO elimination. The appearance energies (AEs) of fragment ions [CH2NHCOCH2]+• and [CH3CHNHCOCHCH3]+• are measured to be 10.21 and 9.66±0.05 eV, respectively, which are formed from cyclo(Gly-Gly) and cyclo(Ala-Ala) radical cations with HNCO elimination. Due to the stabilization of the radical cation of cyclo(Gly-Val) with isopropyl side group, the dominant fragment ion m/z 114 assigned as [C4H6N2O2]+• is produced by γ-H migration and i cleavage to lose propylene. The ionization energies (IEs) of three cyclic dipeptides decrease in the order cyclo(Gly-Gly) (9.33±0.05 eV)>cyclo(Ala-Ala) (9.21±0.05 eV)>cyclo(Gly-Val) (9.09±0.05 eV) from measurements of photoionization efficiency spectra. It implies that IEs of cyclic dipeptides are affected by substituent groups and symmetrical characterization of molecular structures. These observations of the chemical properties of cyclic dipeptides radical ion (M+•) may be important for understanding gas-phase molecular reactivity of 2,5-diketopiperazines and guiding diketopiperazine-based drug design.
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| 21927839 |
Bi-functional peptides with both trypsin-inhibitory and antimicrobial activities are frequent defensive molecules in Ranidae amphibian skins |
10.1007/s00726-011-1079-8. |
Amino Acids |
Bi-functional peptides with both trypsin-inhibitory and antimicrobial activities are frequent defensive molecules in Ranidae amphibian skins
Abstract
- Amphibian skins act as the first line against noxious aggression by microorganisms, parasites, and predators. Anti-microorganism activity is an important task of amphibian skins. A large amount of gene-encoded antimicrobial peptides (AMPs) has been identified from amphibian skins. Only a few of small protease inhibitors have been found in amphibian skins. From skin secretions of 5 species (Odorrana livida, Hylarana nigrovittata, Limctes kuhlii, Odorrana grahami, and Amolops loloensis) of Ranidae frogs, 16 small serine protease inhibitor peptides have been purified and characterized. They have lengths of 17-20 amino acid residues (aa). All of them are encoded by precursors with length of 65-70 aa. These small peptides show strong trypsin-inhibitory abilities. Some of them can exert antimicrobial activities. They share the conserved GCWTKSXXPKPC fragment in their primary structures, suggesting they belong to the same families of peptide. Signal peptides of precursors encoding these serine protease inhibitors share obvious sequence similarity with those of precursors encoding AMPs from Ranidae frogs. The current results suggest that these small serine protease inhibitors are the common defensive compounds in frog skin of Ranidae as amphibian skin AMPs.
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| 21930792 |
SCIMP, a transmembrane adaptor protein involved in major histocompatibility complex class II signaling |
10.1128/MCB.05817-11. |
Mol Cell Biol |
SCIMP, a transmembrane adaptor protein involved in major histocompatibility complex class II signaling
Abstract
- Formation of the immunological synapse between an antigen-presenting cell (APC) and a T cell leads to signal generation in both cells involved. In T cells, the lipid raft-associated transmembrane adaptor protein LAT plays a central role. Its phosphorylation is a crucial step in signal propagation, including the calcium response and mitogen-activated protein kinase activation, and largely depends on its association with the SLP76 adaptor protein. Here we report the discovery of a new palmitoylated transmembrane adaptor protein, termed SCIMP. SCIMP is expressed in B cells and other professional APCs and is localized in the immunological synapse due to its association with tetraspanin-enriched microdomains. In B cells, it is constitutively associated with Lyn kinase and becomes tyrosine phosphorylated after major histocompatibility complex type II (MHC-II) stimulation. When phosphorylated, SCIMP binds to the SLP65 adaptor protein and also to the inhibitory kinase Csk. While the association with SLP65 initiates the downstream signaling cascades, Csk binding functions as a negative regulatory loop. The results suggest that SCIMP is involved in signal transduction after MHC-II stimulation and therefore serves as a regulator of antigen presentation and other APC functions.
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| 21933345 |
Novel lynx spider toxin shares common molecular architecture with defense peptides from frog skin |
10.1111/j.1742-4658.2011.08361.x. |
FEBS J |
Novel lynx spider toxin shares common molecular architecture with defense peptides from frog skin
Abstract
- A unique 30-residue cationic peptide oxyopinin 4a (Oxt 4a) was identified in the venom of the lynx spider Oxyopes takobius (Oxyopidae). Oxt 4a contains a single N-terminally located disulfide bond, Cys4-Cys10, and is structurally different from any spider toxin studied so far. According to NMR findings, the peptide is disordered in water, but assumes a peculiar torpedo-like structure in detergent micelles. It features a C-terminal amphipathic α-helical segment (body; residues 12-25) and an N-terminal disulfide-stabilized loop (head; residues 1-11), and has an unusually high density of positive charge in the head region. Synthetic Oxt 4a was produced and shown to possess strong and broad-spectrum cytolytic and antimicrobial activity. cDNA cloning showed that the peptide is synthesized in the form of a conventional prepropeptide with an acidic prosequence. Unlike other arachnid toxins, Oxt 4a exhibits striking similarity with defense peptides from the skin of ranid frogs that contain the so-called Rana-box motif (a C-terminal disulfide-enclosed loop). Parallelism or convergence is apparent on several levels: the structure, function and biosynthesis of a lynx spider toxin are mirrored by those of Rana-box peptides from frogs.
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