| 19633086 |
Isolation of a variant of subtilosin A with hemolytic activity |
10.1128/JB.00541-09. |
J Bacteriol |
Isolation of a variant of subtilosin A with hemolytic activity
Abstract
- Bacillus subtilis produces an anionic bacteriocin called subtilosin A that possesses antibacterial activity against certain gram-positive bacteria. In this study, we uncovered a hemolytic mutant of B. subtilis that produces an altered form of subtilosin A. The mutant bacteriocin, named subtilosin A1, has a replacement of threonine at position 6 with isoleucine. In addition to the hemolytic activity, subtilosin A1 was found to exhibit enhanced antimicrobial activity against specific bacterial strains. The B. subtilis albB mutant that does not produce a putative immunity peptide was more sensitive to both subtilosin A and subtilosin A1. A spontaneous suppressor mutation of albB that restored resistance to subtilosin A and subtilosin A1 was obtained. The sbr (subtilosin resistance) mutation conferring the resistance is not linked to the sboA-alb locus. The sbr mutation does not increase the resistance of B. subtilis to other cell envelope-targeted antimicrobial agents, indicating that the mutation specifically confers the resistance to subtilosins. The findings suggest possible bioengineering approaches for obtaining anionic bacteriocins with enhanced and/or altered bactericidal activity. Furthermore, future identification of the subtilosin-resistant mutation could provide insights into the mechanism of subtilosin A activity.
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| 19635516 |
Antimicrobial peptides from the skin secretions of the New World frogs Lithobates capito and Lithobates warszewitschii (Ranidae) |
10.1016/j.peptides.2009.07.011. |
Peptides |
Antimicrobial peptides from the skin secretions of the New World frogs Lithobates capito and Lithobates warszewitschii (Ranidae)
Abstract
- Taxonomic revisions within the anuran family Ranidae have established the genus Lithobates that currently comprises 49 species of frogs from the New World. Peptidomic analysis, using reversed-phase HPLC with on-line detection by electrospray mass spectrometry, has led to the identification of multiple antimicrobial peptides in norepinephrine-stimulated skin secretions of the North American frog Lithobates capito and the Central American frog Lithobates warszewitschii. Structural characterization of the peptides demonstrated that the L. capito secretions contained brevinin-1 (1), esculentin-1 (1), esculentin-2 (1), ranatuerin-2 (3), and temporin (2) peptides. L. warszewitschii secretions contained brevinin-1 (1), esculentin-2 (1), ranatuerin-2 (2), and temporin (1) peptides. Values in parentheses indicate number of peptides in each family. Temporin-CPa from L. capito, with the atypical structure IPPFIKKVLTTVF.NH(2), also showed atypical growth-inhibitory activity having greater potency against Escherichia coli (MIC=25 microM) and Candida albicans (MIC=25 microM) than against Staphylococcus aureus (MIC=50 microM). Phylogenetic analysis based upon the amino acid sequences of 37 ranatuerin-2 peptides from 17 species belonging to the genus Lithobates provides support for currently accepted taxonomic relationships. L. capito is sister-group to Lithobates sevosus in a clade that also contains Lithobates areolatus, and Lithobates palustris. L. warszewitschii is most closely related to the Central American species Lithobates tarahumarae and Lithobates vaillanti.
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| 19637889 |
An inhibitor of CCL2-induced chemotaxis from the fungus Leptoxyphium sp |
10.1021/np800745r. |
J Nat Prod |
An inhibitor of CCL2-induced chemotaxis from the fungus Leptoxyphium sp
Abstract
- A biological screen used to identify inhibitors of monocyte chemotactic protein-1 (CCL2)-induced chemotaxis was applied in the activity-guided fractionation of an extract from a fungus of the genus Leptoxyphium sp. Inhibition of CCL2-induced chemotaxis was traced to a new dichlorinated diketopiperazine, cyclo(13,15-dichloro-L-Pro-L-Tyr). A structure-activity relationship (SAR) study evaluating relative activities of cyclo(13,15-dichloro-L-Pro-L-Tyr) and a nonchlorinated homologue cyclo(L-Pro-L-Tyr) showed that the dichlorinated molecule was 10- to 20-fold more active than the nonchlorinated form, while no activity was observed for cyclo(D-N-methylLeu-L-Trp).
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| 19666732 |
Conjugative plasmid from Lactobacillus gasseri LA39 that carries genes for production of and immunity to the circular bacteriocin gassericin A |
10.1128/AEM.00195-09. |
Appl Environ Microbiol |
Conjugative plasmid from Lactobacillus gasseri LA39 that carries genes for production of and immunity to the circular bacteriocin gassericin A
Abstract
- Gassericin A is a circular bacteriocin produced by Lactobacillus gasseri strain LA39. We found a 33,333-bp plasmid, designated pLgLA39, in this strain. pLgLA39 contained 44 open reading frames, including seven genes related to gassericin A production/immunity (gaa), as well as genes for replication, plasmid maintenance, and conjugative transfer. pLgLA39 was transferred from LA39 to the type strain of L. gasseri (JCM 1131) by filter mating. The transconjugant exhibited >30-fold-higher more resistance to gassericin A and produced antibacterial activity. Lactobacillus reuteri LA6, the producer of reutericin 6, was proved to harbor a plasmid indistinguishable from pLgLA39 and carrying seven genes 100% identical to gaa. This suggests that pLgLA39 might have been transferred naturally between L. gasseri LA39 and L. reuteri LA6. The seven gaa genes of pLgLA39 were cloned into a plasmid vector to construct pGAA. JCM 1131(T) transformed with pGAA expressed antibacterial activity and resistance to gassericin A. pGAA was segregationally more stable than a pGAA derivative plasmid from which gaaA was deleted and even was more stable than the vector. This suggests the occurrence of postsegregational host killing by the gaa genes. pLgLA39 carried a pemIK homolog, and segregational stabilization of a plasmid by the pLgLA39-type pemIK genes was also confirmed. Thus, pLgLA39 was proved to carry the genes for at least two plasmid maintenance mechanisms, i.e., gaa and pemIK. Plasmids containing a repA gene similar to pLgLA39 repA were distributed in several L. gasseri strains.
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| 19679485 |
Structural and biological evaluation of some loloatin C analogues |
10.1016/j.bmc.2009.07.049. |
Bioorg Med Chem |
Structural and biological evaluation of some loloatin C analogues
Abstract
- Loloatin C is a cyclic cationic antimicrobial peptide which is active against gram positive as well as certain gram negative bacteria. Unfortunately, it is equally potent against human erythrocytes. To probe the structure-activity relationship of this promising antibiotic peptide, amino acid substitution and/or incorporation of a constraint sugar amino acid dipeptide isoster has been applied. Six new derivatives have been synthesized using SPPS and their solution structure investigated using NMR studies. Finally, the antimicrobial and the hemolytic activities have been determined.
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| 19680927 |
Structural analysis of enniatin H, I, and MK1688 and beauvericin by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and their production by Fusarium oxysporum KFCC 11363P |
10.1080/02652030802562904. |
Food Addit Contam Part A Chem Anal Control Expo Risk Assess |
Structural analysis of enniatin H, I, and MK1688 and beauvericin by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and their production by Fusarium oxysporum KFCC 11363P
Abstract
- The molecular structures of enniatins H, I, and MK1688 and beauvericin were investigated by liquid chromatography-tandem mass spectrometry (LC-MS/MS). MS fragmentation occurred by loss of -CO after opening of the cyclic molecule to carbonyl carbon, and cleavage of the peptide and ester bonds in the molecular structure. Fusarium oxysporum KFCC 11363P was tested for its ability to produce beauvericin and enniatins H, I, and MK1688 on five cereal substrates: rice, barley, maize, wheat, and Indian millet kernels. Furthermore, optimal conditions for the production of the four mycotoxins by the Fusarium isolate were examined on maize at four temperatures (15, 20, 25, and 30 degrees C) and at three moisture contents (10, 20, and 40%). Large amounts of beauvericin and enniatin H were present in maize cultures at 25 degrees C (232.4 and 196.4 microg g(-1), respectively). Enniatins I and MK1688 were maximally formed at 20 degrees C (221.5 and 180.2 microg g(-1), respectively). The optimal moisture contents for the production of enniatins H (196.4 microg g(-1)) and MK1688 (165.6 microg g(-1)), were 40%.
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| 19690332 |
Quantitative phosphoproteomic analysis of T cell receptor signaling reveals system-wide modulation of protein-protein interactions. |
10.1126/scisignal.2000007 |
Sci. Signal. |
Quantitative phosphoproteomic analysis of T cell receptor signaling reveals system-wide modulation of protein-protein interactions.
Abstract
- Protein phosphorylation events during T cell receptor (TCR) signaling control the formation of complexes among proteins proximal to the TCR, the activation of kinase cascades, and the activation of transcription factors; however, the mode and extent of the influence of phosphorylation in coordinating the diverse phenomena associated with T cell activation are unclear. Therefore, we used the human Jurkat T cell leukemia cell line as a model system and performed large-scale quantitative phosphoproteomic analyses of TCR signaling. We identified 10,665 unique phosphorylation sites, of which 696 showed TCR-responsive changes. In addition, we analyzed broad trends in phosphorylation data sets to uncover underlying mechanisms associated with T cell activation. We found that, upon stimulation of the TCR, phosphorylation events extensively targeted protein modules involved in all of the salient phenomena associated with T cell activation: patterning of surface proteins, endocytosis of the TCR, formation of the F-actin cup, inside-out activation of integrins, polarization of microtubules, production of cytokines, and alternative splicing of messenger RNA. Further, case-by-case analysis of TCR-responsive phosphorylation sites on proteins belonging to relevant functional modules together with network analysis allowed us to deduce that serine-threonine (S-T) phosphorylation modulated protein-protein interactions (PPIs) in a system-wide fashion. We also provide experimental support for this inference by showing that phosphorylation of tubulin on six distinct serine residues abrogated PPIs during the assembly of microtubules. We propose that modulation of PPIs by stimulus-dependent changes in S-T phosphorylation state is a widespread phenomenon applicable to many other signaling systems.
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| 19692336 |
The three-dimensional structure of carnocyclin A reveals that many circular bacteriocins share a common structural motif |
10.1074/jbc.M109.036459. |
J Biol Chem |
The three-dimensional structure of carnocyclin A reveals that many circular bacteriocins share a common structural motif
Abstract
- Carnocyclin A (CclA) is a potent antimicrobial peptide from Carnobacterium maltaromaticum UAL307 that displays a broad spectrum of activity against numerous Gram-positive organisms. An amide bond links the N and C termini of this bacteriocin, imparting stability and structural integrity to this 60-amino acid peptide. CclA interacts with lipid bilayers in a voltage-dependent manner and forms anion selective pores. Several other circular bacteriocins have been reported, yet only one (enterocin AS-48) has been structurally characterized. We have now determined the solution structure of CclA by NMR and further examined its anion binding and membrane channel properties. The results reveal that CclA preferentially binds halide anions and has a structure that is surprisingly similar to that of AS-48 despite low sequence identity, different oligomeric state, and disparate function. CclA folds into a compact globular bundle, comprised of four helices surrounding a hydrophobic core. NMR studies show two fluoride ion binding modes for CclA. Our findings suggest that although other circular bacteriocins are likely to have diverse mechanisms of action, many may have a common structural motif. This shared three-dimensional arrangement resembles the fold of mammalian saposins, peptides that either directly lyse membranes or serve as activators of lipid-degrading enzymes.
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| 19706788 |
Differential efficacy of SSTR1, -2, and -5 agonists in the inhibition of C6 glioma growth in nude mice |
10.1152/ajpendo.00292.2009. |
Am J Physiol Endocrinol Metab |
Differential efficacy of SSTR1, -2, and -5 agonists in the inhibition of C6 glioma growth in nude mice
Abstract
- Somatostatin receptors (SSTR1-5) mediate antiproliferative effects. In C6 rat glioma cells, somatostatin is cytostatic in vitro via phosphotyrosine phosphatase-dependent inhibition of ERK1/2 activity mediated by SSTR1, -2, and -5. Here we analyzed the effects of SSTR activation on C6 glioma growth in vivo and the intracellular mechanisms involved, comparing somatostatin effects with selective agonists for SSTR1, -2, and -5 (BIM-23745, BIM-23120, BIM-23206) or receptor biselective compounds (SSTR1 and -2, BIM-23704; and SSTR2 and -5, BIM-23190). Nude mice subcutaneously xenografted with C6 cells were treated with somatostatin, SSTR agonists (50 μg, twice/day), or vehicle. Tumor growth was evaluated every 3 days for 19 days. The intracellular pathways responsible of SSTR effects in vivo were evaluated measuring Ki-67, phospho-ERK1/2, and p27(kip1) expression by immunohistochemistry in sections from explanted tumors. Somatostatin and SSTR1, -2, and -5 agonists strongly inhibited in vivo C6 tumor growth, intratumoral neovessel formation, Ki-67 expression, and ERK1/2 phosphorylation and induced upregulation of p27(Kip1), whereas only a modest activation of caspase-3 was observed. Somatostatin (acting on SSTR1, -2, and -5) displayed the highest efficacy; SSTR5 selective agonist showed a stronger effect than SSTR1 agonist, and SSTR2 agonist was less effective. On the other hand, SSTR1 and -2 agonists maximally reduced tumor neovascularization. The combined activation of SSTR1 and -2 showed a synergistic activity, reaching a higher efficacy than BIM-23206, whereas the simultaneous activation of SSTR2 and -5 resulted in a response resembling SSTR5 effects. Thus the simultaneous activation of different SSTRs inhibits glioma cell proliferation in vivo through both direct cytotostatic and antiangiogenic effects.
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| 19707378 |
Lepirudin in the management of patients with heparin-induced thrombocytopenia |
10.2147/btt.s3415. |
Biologics |
Lepirudin in the management of patients with heparin-induced thrombocytopenia
Abstract
- Lepirudin, a recombinant hirudin, is a direct irreversible thrombin inhibitor by binding to both free and clot-bound thrombin. It is approved for treatment of heparin-induced thrombocytopenia (HIT), which is a serious antibody-mediated drug reaction mostly associated with the use of unfractionated heparin. Clinical experience during the last 10 years has proved the efficacy of lepirudin in the management of HIT. The major route of elimination of lepirudin is the kidney, accounting for approximately 90% of its systemic clearance. The most important adverse reactions are bleeding and the induction of immunologic reactions. The risk of bleeding can be reduced by implementing an optimal monitoring and dose adjustment strategy, particularly in patients undergoing cardiopulmonary bypass surgery and in those with impaired renal function. Development of antihirudin antibodies may enhance the anticoagulant effect of lepirudin. Anaphylactic reactions associated with lepirudin therapy are rare. The lack of an antidote against lepirudin is still a concern, particularly during cardiopulmonary bypass surgery with a heart-lung machine and during artificial renal support. Currently, hemofiltration using high-flux filter systems is the only available and valid means to manage hirudin overdose. Nevertheless, the drug can be safely used if meticulous monitoring strategy is installed.
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| 19724014 |
Echinocandins: the newest class of antifungals |
10.1345/aph.1M237. |
Ann Pharmacother |
Echinocandins: the newest class of antifungals
Abstract
- To review the mechanism of action, antifungal spectrum of activity, pharmacodynamics, pharmacokinetics, clinical efficacy, and safety of the echinocandins.
A MEDLINE search (1982-May 2009) was conducted for articles published in the English language using the key words caspofungin, micafungin, anidulafungin, and echinocandins.
Medicinal chemistry, in vitro, and animal studies, as well as human trials were reviewed for information on the pharmacodynamics, pharmacokinetics, efficacy, and safety of each echinocandin. Clinical trials were reviewed and included to compare and contrast the available echinocandins.
Three echinocandin antifungal agents are currently approved for use in the US: caspofungin, micafungin, and anidulafungin. The echinocandins have a unique mechanism of action, inhibiting beta-(1,3)-D-glucan synthase, an enzyme that is necessary for the synthesis of an essential component of the cell wall of several fungi. The echinocandins display fungistatic activity against Aspergillus spp. and fungicidal activity against most Candida spp., including strains that are fluconazole-resistant. The echinocandins have been shown to be efficacious for the treatment of esophageal candidiasis, candidemia, and invasive candidiasis. In addition, caspofungin has demonstrated efficacy as empiric treatment of febrile neutropenia and salvage therapy for the treatment of invasive aspergillosis, and it is the only echinocandin approved for use in pediatric patients. Micafungin is the only echinocandin approved for use as prophylaxis against Candida infections in patients undergoing hematopoietic stem cell transplantation. Overall, resistance to echinocandins is still rare, and all agents are well tolerated, with similar adverse effect profiles and few drug-drug interactions.
Echinocandins, the newest addition to the arsenal of antifungals, offer potential advantages over other classes of agents. Clinicians should assess their distinguishing characteristics, including route of metabolism, drug interaction profile, and approved indications for use, when determining which agent to include on a formulary.
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| 19725875 |
Common G102S polymorphism in chitotriosidase differentially affects activity towards 4-methylumbelliferyl substrates. |
10.1111/j.1742-4658.2009.07259.x |
FEBS J. |
Common G102S polymorphism in chitotriosidase differentially affects activity towards 4-methylumbelliferyl substrates.
Abstract
- Chitotriosidase (CHIT1) is a chitinase that is secreted by activated macrophages. Plasma chitotriosidase activity reflects the presence of lipid-laden macrophages in patients with Gaucher disease. CHIT1 activity can be conveniently measured using fluorogenic 4-methylumbelliferyl (4MU)-chitotrioside or 4MU-chitobioside as the substrate, however, nonsaturating concentrations have to be used because of apparent substrate inhibition. Saturating substrate concentrations can, however, be used with the newly designed substrate 4MU-deoxychitobioside. We studied the impact of a known polymorphism, G102S, on the catalytic properties of CHIT1. The G102S allele was found to be common in type I Gaucher disease patients in the Netherlands ( approximately 24% of alleles). The catalytic efficiency of recombinant Ser102 CHIT1 was approximately 70% that of wild-type Gly102 CHIT1 when measured with 4MU-chitotrioside at a nonsaturating concentration. However, the activity was normal with 4MU-deoxychitobioside as the substrate at saturating concentrations, consistent with predictions from molecular dynamics simulations. In conclusion, interpretation of CHIT1 activity measurements with 4MU-chitotrioside with respect to CHIT1 protein concentrations depends on the presence of Ser102 CHIT1 in an individual, complicating estimation of the body burden of storage macrophages. Use of the superior 4MU-deoxychitobioside substrate avoids such complications because activity towards this substrate under saturating conditions is not affected by the G102S substitution.
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| 19743810 |
Isolation and structural elucidation of euryjanicins B-D, proline-containing cycloheptapeptides from the Caribbean marine sponge Prosuberites laughlini |
10.1021/np9004135. |
J Nat Prod |
Isolation and structural elucidation of euryjanicins B-D, proline-containing cycloheptapeptides from the Caribbean marine sponge Prosuberites laughlini
Abstract
- Three new cyclic peptides, euryjanicins B (2), C (3), and D (4), have been isolated from the Puerto Rican marine sponge Prosuberites laughlini, and the structures were elucidated by chemical degradation, ESIMS/MS, and extensive 2D NMR methods. When tested against the National Cancer Institute 60 tumor cell line panel, all of the purified isolates displayed weak cytotoxicity.
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| 19748593 |
A pharmacokinetic study of plerixafor in subjects with varying degrees of renal impairment |
10.1016/j.bbmt.2009.09.003. |
Biol Blood Marrow Transplant |
A pharmacokinetic study of plerixafor in subjects with varying degrees of renal impairment
Abstract
- Plerixafor is a selective antagonist of CXCR4 used for mobilization of hematopoietic stem cells (HSCs) for autologous stem cell transplantation (SCT) in patients with multiple myeloma (MM) and non-Hodgkin lymphoma (NHL). This Phase 1 open-label study in healthy subjects was conducted to evaluate the pharmacokinetic characteristics of plerixafor in subjects with renal impairment. All subjects received a single 0.24 mg/kg subcutaneous dose of plerixafor. Subjects were stratified into 4 cohorts based on creatinine clearance determined from a 24-hour urine collection: control (>90 mL/min), mild renal impairment (51-80 mL/min), moderate renal impairment (31-50 mL/min), and severe renal impairment (<31 mL/min, not requiring dialysis). Eleven female subjects (48%) and 12 male subjects (52%), ranging in age from 35 to 73 years, were enrolled. Plerixafor clearance was reduced in subjects with renal impairment and was positively correlated with creatinine clearance. The mean area under the concentration- versus-time curve from time 0 to 24 hours postdose of plerixafor in subjects with mild, moderate, and severe renal impairment was 7%, 32%, and 39% higher, respectively, than that in subjects with normal renal function. Renal impairment had no effect on maximal plasma concentrations. The safety profile was similar among subjects with renal impairment and controls. No renal impairment-related trends in the incidence of adverse events were apparent. A plerixaflor dose reduction to 160 microg/kg in patients with a creatinine clearance value <or= 50 mL/min is expected to result in exposure similar to that in patients with normal to mildly impaired renal function.
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| 19749156 |
G protein-coupled receptor 30 expression is up-regulated by EGF and TGF alpha in estrogen receptor alpha-positive cancer cells |
10.1210/me.2009-0120. |
Mol Endocrinol |
G protein-coupled receptor 30 expression is up-regulated by EGF and TGF alpha in estrogen receptor alpha-positive cancer cells
Abstract
- In the present study, we evaluated the regulation of G protein-coupled receptor (GPR)30 expression in estrogen receptor (ER)-positive endometrial, ovarian, and estrogen-sensitive, as well as tamoxifen-resistant breast cancer cells. We demonstrate that epidermal growth factor (EGF) and TGF alpha transactivate the GPR30 promoter and accordingly up-regulate GPR30 mRNA and protein levels only in endometrial and tamoxifen-resistant breast cancer cells. These effects exerted by EGF and TGF alpha were dependent on EGF receptor (EGFR) expression and activation and involved phosphorylation of the Tyr(1045) and Tyr(1173) EGFR sites. Using gene-silencing experiments and specific pharmacological inhibitors, we have ascertained that EGF and TGF alpha induce GPR30 expression through the EGFR/ERK transduction pathway, and the recruitment of c-fos to the activator protein-1 site located within GPR30 promoter sequence. Interestingly, we show that functional cross talk of GPR30 with both activated EGFR and ER alpha relies on a physical interaction among these receptors, further extending the potential of estrogen to trigger a complex stimulatory signaling network in hormone-sensitive tumors. Given that EGFR/HER2 overexpression is associated with tamoxifen resistance, our data may suggest that ligand-activated EGFR could contribute to the failure of tamoxifen therapy also by up-regulating GPR30, which in turn could facilitates the action of estrogen. In addition, important for resistance is the ability of tamoxifen to bind to and activate GPR30, the expression of which is up-regulated by EGFR activation. Our results emphasize the need for new endocrine agents able to block widespread actions of estrogen without exerting any stimulatory activity on transduction pathways shared by the steroid and growth factor-signaling networks.
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