摘要:

We present the antimicrobial and hemolytic activities of the decapeptide anoplin and 19 analogs thereof tested against methicillin‐resistantStaphylococcus aureusATCC 33591 (MRSA),Escherichia coli(ATCC 25922),Pseudomonas aeruginosa(ATCC 27853), vancomycin‐resistantEnterococcus faecium(ATCC 700221) (VRE), andCandida albicans(ATCC 200955). The anoplin analogs contain substitutions in amino acid positions 2, 3, 5, 6, 8, 9, and 10. We use these peptides to study the effect of altering the charge and hydrophobicity of anoplin on activity against red blood cells and microorganisms. We find that increasing the charge and/or hydrophobicity improves antimicrobial activity and increases hemolytic activity. For each strain tested, we identify at least six anoplin analogs with an improved therapeutic index compared with anoplin, the only exception beingEnterococcus faecium, against which only few compounds are more specific than anoplin. Both 2Nal6and Cha6show improved therapeutic index against all strains tested. Copyright © 2013 European Peptide Society and John Wiley&Sons,

ISSN:1075-2617    

DOI:10.1002/psc.2548

年代:2013

数据来源: WILEY

摘要:

Id proteins, inhibitors of DNA binding proteins, have highly conserved dimerization motif known as the helix‐loop‐helix (HLH) domain that acts as a negative regulator of basic HLH (bHLH) transcription factors. In signaling pathways, Id proteins play an important role in cellular development, proliferation, and differentiation. The mechanism of Id proteins is to antagonize bHLH proteins, thereby preventing them from binding to DNA and inhibiting transcription of cellular differentiation‐associated genes in cancer. Recently, we reported an inhibitor of Id1, peptide 3C, which showed good affinity to Id1 protein and exhibited inhibitory effects in cancer cells. In this study, Ala (A)‐substituted analogs of peptide 3C were synthesized by SPPS, purified by RP‐HPLC, and characterized by MALDI‐TOF MS. Binding of each peptide to Id1 or Id1‐HLH (the HLH domain of Id1) was monitored by surface plasmon resonance (SPR)‐based biosensor. Biological effect of each peptide in MCF‐7 breast cancer cells was analyzed by MTT cell viability assay. The secondary structure of substituted analogs of peptide 3C was investigated by circular dichroism (CD) spectroscopy. SPR results revealed that A‐substituted analogs of peptide 3C showed weaker binding to Id1 than that of peptide 3C, indicating that the six amino acid residues in theN‐terminal of peptide 3C were all essential for binding to Id1 and the importance of amino acid residue was I2 > Q6 > Y1 > G4 > L5 > E3. In addition, substitution of E3in peptide 3C with D, Q, and R did not improve the binding potency of peptide 3C. MTT assay demonstrated that neither A‐substituted nor position 3‐substituted analogs of peptide 3C showed increased antiproliferative effect in MCF‐7 cancer cells. CD results indicated that peptide 3C exhibited the highest content ofα‐helical structure (39.37%), suggesting that theα‐helical structure may contribute to its binding potency for Id1 and Id1‐HLH. SAR results provided important information for the development of peptidic inhibitors of Id1 as anticancer agents and demonstrated peptide 3C as a promising lead for further modifications. Copyright

ISSN:1075-2617    

DOI:10.1002/psc.2549

年代:2013

数据来源: WILEY

摘要:

It has been reported that obestatin regulates adipocyte metabolism via receptors on the cell surface. We wondered whether obestatin can interact with intracellular components that activated signalling pathways in adipocytes. Because obestatin (human) only presents one lysine (at position 10), which cannot penetrate the cell membrane, therefore, we used a cell‐permeable peptide TAT (49‐57) as a vector to carry obestatin across the cell membrane. The goal of this study was to further understand the function of obestatin after penetrating the cell membrane. Our results showed that TAT‐obestatin could cross the 3T3‐L1 cell membrane in the absence of cytotoxicity. TAT‐obestatin showed no effect on the proliferation of 3T3‐L1 preadipocytes. In contrast, obestatin significantly stimulated proliferation at a dose of 10‐11 M and 10‐13 M. In addition, TAT‐obestatin demonstrated a more potent inhibitory effect on cell apoptosis induced by serum starvation than that of obestatin. During the progress of adipocyte differentiation, TAT‐obestatin and obestatin had no effect on adipogenesis. In the lipolysis assay, TAT‐obestatin significantly increased glycerol and free fatty acid release from 3T3‐L1 adipocytes after 3 h treatment but showed no significant effect on lipolysis after 24 h and 48 h of treatment. In contrast, obestatin (10‐7 M) had no effect on glycerol release after 3, 24 and 48 h of treatment. The difference between the effect of TAT‐obestatin and obestatin on adipocytes metabolism indicated that TAT‐obestatin may trigger intracellular signalling as well as signalling at the cell membrane. Copyright © 2013 Europ

ISSN:1075-2617    

DOI:10.1002/psc.2550

年代:2013

数据来源: WILEY

摘要:

Herein, we describe a scalable purification of the lantibiotic nisin via an extraction/precipitation approach using a biphasic system, which can be carried out up to 40–80 gram scale. This approach results in an at least tenfold enrichment of commercially available preparations of nisin, which usually contain only 2.5% of the desired peptide, to allow further purification by preparative HPLC. As a follow‐up study, the enriched nisin sample was digested either by trypsin or chymotrypsin, or treated by CNBr, and these reactions were monitored by LC‐MS to identify and characterize the obtained fragments. Two previously unknown cleavage sites have been identified: Asn20–Met21 and Met21–Lys22 for trypsin and chymotrypsin, respectively. Furthermore, a novel and convenient enzymatic approach to isolate the native nisin C‐ring [nisin fragment (13–20)] was uncovered. Finally, by means of preparative HPLC, nisin fragments (1–12), (1–20), (22–34), and (22–31) could be isolated and will be used in a semi‐synthesis approach to elucidate the role of each fragment in the mode of action of nisin as an antimicrobial peptide. Copyright © 2013 European Peptide Society

ISSN:1075-2617    

DOI:10.1002/psc.2551

年代:2013

数据来源: WILEY

摘要:

KR‐12 (residues 18–29 of LL‐37) was known to be the smallest peptide of human cathelicidin LL‐37 possessing antimicrobial activity. In order to optimize α‐helical short antimicrobial peptides having both antimicrobial and antiendotoxic activities without mammalian cell toxicity, we designed and synthesized a series of KR‐12 analogs. Highest hydrophobic analogs KR‐12‐a5 and KR‐12‐a6 displayed greater inhibition of lipopolysaccharide (LPS)‐stimulated tumor necrosis factor‐α production and higher LPS‐binding activity. We have observed that antimicrobial activity is independent of charge, but LPS neutralization requires a balance of hydrophobicity and net positive charge. Among KR‐12 analogs, KR‐12‐a2, KR‐12‐a3 and KR‐12‐a4 showed much higher cell specificity for bacteria over erythrocytes and retained antiendotoxic activity, relative to parental LL‐37. KR‐12‐a5 displayed the strongest antiendotoxic activity but almost similar cell specificity as compared with LL‐37. Also, these KR‐12 analogs (KR‐12‐a2, KR‐12‐a3, KR‐12‐a4 and KR‐12‐a5) exhibited potent antimicrobial activity (minimal inhibitory concentration: 4 μM) against methicillin‐resistantStaphylococcus aureus. Taken together, these KR‐12 analogs have the potential for future development as a novel class of antimicrobial and anti‐inflammatory therapeuti

ISSN:1075-2617    

DOI:10.1002/psc.2552

年代:2013

数据来源: WILEY

摘要:

Self‐assembly of natural or designed peptides into fibrillar structures based onβ‐sheet conformation is a ubiquitous and important phenomenon. Recently, organic solvents have been reported to play inductive roles in the process of conformational change and fibrillization of some proteins and peptides. In this study, we report the change of secondary structure and self‐assembling behavior of the surfactant‐like peptide A6K at different ethanol concentrations in water. Circular dichroism indicated that ethanol could induce a gradual conformational change of A6K from unordered secondary structure toβ‐sheet depending upon the ethanol concentration. Dynamic light scattering and atomic force microscopy revealed that with an increase of ethanol concentration the nanostructure formed by A6K was transformed from nanosphere/string‐of‐beads to long and smooth fibrils. Furthermore, Congo red staining/binding and thioflavin‐T binding experiments showed that with increased ethanol concentration, the fibrils formed by A6K exhibited stronger amyloid fibril features. These results reveal the ability of ethanol to promoteβ‐sheet conformation and fibrillization of the surfactant‐like peptide, a fact that may be useful for both designing self‐assembling peptide nanomaterials and clarifying the molecular mechanism behind the formation of amyloid fibrils. Copyright © 2013 European Peptide Society

ISSN:1075-2617    

DOI:10.1002/psc.2553

年代:2013

数据来源: WILEY

摘要:

Sphingosine‐1‐phosphate (S1P) is a bioactive lipid with key functions in the immune, inflammatory, and cardiovascular systems. S1P exerts its action through the interaction with a family of five known G protein‐coupled receptors, named S1P1–5. Among them, S1P3has been implicated in the pathological processes of a number of diseases, including sepsis and cancer. KRX‐725 (compound 1) is a pepducin that mimics the effects of S1P by triggering specifically S1P3. Here, aiming to identify novel S1P3antagonists, we carried out an alanine scanning analysis to address the contribution of the side chains of each amino acid residue to the peptide function. Then, deleted peptides from both the C‐ and N‐terminus were prepared in order to determine the minimal sequence for activity and to identify the structural requirements for agonistic and, possibly, antagonistic behaviors. The pharmacological results of the Ala‐scan derived compounds (2–10) suggested a high tolerance of the pepducin 1 to amino acid substitutions. Importantly, the deleted peptide 16 has the ability to inhibit, in a dose‐dependent manner, both pepducin 1‐induced vasorelaxation and fibroblast proliferation. Finally, a computational analysis was performed on the prepared compounds, showing that the supposed antagonists 16 and 17 appeared to be aligned with each other but not with the others. These results suggested a correlation between specific conformations and activities. Copyright © 2013 European Peptide Society an

ISSN:1075-2617    

DOI:10.1002/psc.2554

年代:2013

数据来源: WILEY