John Barrett - Academia.edu (original) (raw)

Papers by John Barrett

Expert Opin Investig Drugs, 1994

Journal of Medicinal Chemistry, Nov 1, 1997

A practical combination of comparative modeling and NMR spectroscopy was used to generate a three... more A practical combination of comparative modeling and NMR spectroscopy was used to generate a three-dimensional structure of the response regulator protein, Spo0F. The backbone structure obtained compares to the Spo0F Y13S mutant X-ray structure with an rmsd of 2.0 Å. We provide results which suggest that structures obtained by this method are suitable for drug discovery. The results of the GRID and DOCK methods as applied to the model and X-ray structures of Spo0F are remarkably similar and tend to suggest the same design conclusions. This trend is illustrated by these same techniques applied to two experimentally derived structures of the analogous protein, CheY, which exhibit a pairwise rmsd BB on the same order as that found for the two Spo0F structures.

Antimicrobial Agents and Chemotherapy, 2004

Nocathiacins are cyclic thiazolyl peptides with inhibitory activity against gram-positive bacteri... more Nocathiacins are cyclic thiazolyl peptides with inhibitory activity against gram-positive bacteria. BMS-249524 (nocathiacin I), identified from screening a library of compounds against a multiply antibiotic-resistant Enterococcus faecium strain, was used as a lead chemotype to obtain additional structurally related compounds. The MIC assay results of BMS-249524 and two more water-soluble derivatives, BMS-411886 and BMS-461996, revealed potent in vitro activities against a variety of gram-positive pathogens including methicillin-resistant Staphylococcus aureus, penicillin-resistant Streptococcus pneumoniae, vancomycin intermediate-resistant S. aureus, vancomycin-resistant enterococci, Mycobacterium tuberculosis and Mycobacterium avium. Analysis of killing kinetics revealed that these compounds are bactericidal for S. aureus with at least a 3-log 10 reduction of bacterial growth within 6 h of exposure to four times the MICs. Nocathiacin-resistant mutants were characterized by DNA sequence analyses. The mutations mapped to the rplK gene encoding the L11 ribosomal protein in the 50S subunit in a region previously shown to be involved in the binding of related thiazolyl peptide antibiotics. These compounds demonstrated potential for further development as a new class of antibacterial agents with activity against key antibiotic-resistant gram-positive bacterial pathogens.

Experimental Parasitology, Mar 1, 1992

The biochemical properties of the enzyme responsible for nematode "activated L-serine su... more The biochemical properties of the enzyme responsible for nematode "activated L-serine sulphydrase" activity (L-cysteine + R-SH----cysteine thioether + H2S) have been investigated using primarily the gastro-intestinal nematodes Nippostrongylus brasiliensis and Haemonchus contortus. The activated L-serine sulphydrase enzyme was found to be cytosolic in origin and exhibited maximal activity at pH 9.0. Enzyme activity was widely distributed amongst the major tissues of adult female Ascaris suum but was particularly abundant in longitudinal muscle. The enzyme appeared to have a rigid specificity for L-cysteine as the primary thiol substrate, but was capable of utilising a number of sulphur amino acids (and derivatives) and nonphysiological thiols as second substrates. The best second thiol substrates were nonphysiological, hydroxyl-containing thiols that showed some structural similarity to the standard second substrate, 2-mercaptoethanol. Kinetic analyses revealed that the enzyme operates by a sequential catalytic mechanism, and the absolute Michaelis constants were: KL-cysteine = 0.21 +/- 0.02 mM and K2-mercaptoethanol = 5.58 +/- 0.59 mM. The enzyme was relatively insensitive to inhibition by a variety of substrate analogues and known inhibitors of pyridoxal 5'-phosphate dependent enzymes, whilst plant phenols caused significant levels of inhibition. The most potent inhibitors discovered were the anthelmintics bithionol, dichlorophene and hexachlorophene. Further characterisation revealed that hexachlorophene was a parabolic competitive inhibitor of the activated L-serine sulphydrase enzyme.

Expert Opin Investig Drugs, 1996

Antimicrobial Agents and Chemotherapy, 2002

The antistaphylococcal activities of BMS-284756 (T-3811ME), levofloxacin, moxifloxacin, and cipro... more The antistaphylococcal activities of BMS-284756 (T-3811ME), levofloxacin, moxifloxacin, and ciprofloxacin were compared against wild-type and grlA and grlA/gyrA mutant strains of Staphylococcus aureus. BMS-284756 was the most active quinolone tested, with MICs and minimal bactericidal concentrations against S. aureus wild-type strain MT5, grlA mutant MT5224c4, and grlA/gyrA mutant EN8 of 0.03 and 0.06, 0.125 and 0.125, and 4 and 4 g/ml, respectively. In the time-kill studies, BMS-284756 and levofloxacin exhibited rapid killing against all strains. Ciprofloxacin, however, was not bactericidal for the double mutant, EN8. BMS-284756 and levofloxacin were bactericidal (3 log 10 decrease in CFU/ml) against the MT5 and MT5224c4 strains at two and four times the MIC within 2 to 4 h. Against EN8, BMS-284756 was bactericidal within 4 h at two and four times the MIC, and levofloxacin achieved similar results within 4 to 6 h. Both the wild-type strain MT5 and grlA mutant MT5224c4 should be considered susceptible to both BMS-284756 and levofloxacin, and both quinolones are predicted to have clinical efficacy. The in vivo efficacy of BMS-284756, levofloxacin, and moxifloxacin against S. aureus strain ISP794 and its single mutant 2C6(1)-1 directly reflected the in vitro activity: increased MICs correlated with decreased in vivo efficacy. The 50% protective doses of BMS-284756 against wild-type and mutant strains were 2.2 and 1.6 mg/kg of body weight/day, respectively, compared to the levofloxacin values of 16 and 71 mg/kg/day and moxifloxacin values of 4.7 and 61.6 mg/kg/day. BMS-284756 was more potent than levofloxacin and equipotent with moxifloxacin against ISP794 both in vitro and in vivo, while BMS-284756 was more potent than levofloxacin and moxifloxacin against 2C6(1)-1.

Exp Parasitol, 1992

Characterization of the physical and catalytic properties of the enzyme responsible for nematode ... more Characterization of the physical and catalytic properties of the enzyme responsible for nematode "activated L-serine sulfhydrase" activity (L-cysteine + R-SH-->cysteine thioether + H2S) has led to its identification as a novel, variant form (allelozyme) of cystathionine beta-synthase that is distinct from a mammalian-type synthase also present in nematodes. Additional work has demonstrated the ability of live Panagrellus redivivus to produce H2[35S] from exogenous L-[35S]cysteine and 2-mercaptoethanol, thus providing preliminary evidence for the in vivo operation of the activated L-serine sulfhydrase reaction in nematodes.

Oral levofloxacin was compared to oral ciprofloxacin in a Staphylococcus aureus subcutaneous absc... more Oral levofloxacin was compared to oral ciprofloxacin in a Staphylococcus aureus subcutaneous abscess model in rabbits. Rabbits were surgically prepared with subcutaneous wiffle balls (43 mm in diameter) and allowed to recover for 4 to 6 weeks. Rabbits were infected by direct injection into the capsule with S. aureus ATCC 29213 (5 ؋ 10 5 CFU) and were allowed to remain infected for 8 days before the initiation of anti-infective treatment. Efficacy was determined by assessing the bacterial load within the capsule over a 10-day treatment period. In single-dose pharmacokinetic studies in infected rabbits, similar area under the concentration-time curve/MIC ratios were obtained in the plasma and abscess fluid for levofloxacin at 45 mg/kg of body weight and ciprofloxacin at 200 mg/kg of body weight. Similar efficacies were seen with levofloxacin at 45 mg/kg/day and ciprofloxacin 400 mg/kg/day by day 10. In this model, levofloxacin was significantly more efficacious than ciprofloxacin (P < 0.01).

Journal of animal science, 2002

Photoperiod modulates reproduction in goats. We tested the hypothesis that the excitatory glutama... more Photoperiod modulates reproduction in goats. We tested the hypothesis that the excitatory glutamatergic tone is reduced in the photoinhibited goat. The objectives of this study were to determine the effect of photoperiod and glutamatergic stimulation on LH, GH, and testosterone (T) secretion in goat bucks. Eight mature, intact bucks were used in two simultaneous 4 x 4 Latin square designs. Variables were two photoperiod regimens (short day; SD, 10 h light:14 h dark, n = 4; vs long day; LD, 16 h light:8 h dark, n = 4) and four doses of N-methyl-D-L-aspartate (NMA; 0, 1, 2 and 4 mg/kg BW, i.v.). Venous blood was obtained for 2 h before and after NMA injection, followed by GnRH injection and then a final 1 h of sampling. Injection of NMA increased (P < 0.002) LH secretion within 20 min. This increase was sustained for 120 min, but the response was most pronounced in LD goats. The increase in mean LH was associated with a concomitant dose-dependent increase in pulse frequency (P <...

Antimicrobial agents and chemotherapy, 1998

The c-Myc oncogenic transcription factor heterodimerizes with Max, binds specific DNA sites and r... more The c-Myc oncogenic transcription factor heterodimerizes with Max, binds specific DNA sites and regulates transcription. The role of Myc in transcriptional activation involves its binding to TRRAP and histone acetylases; however, Myc's ability to activate transcription in transient transfection assays is remarkably weak (2 to 5 fold) when compared to other transcription factors. Since a deletion Myc mutant D106-143 and a substitution mutant W135E that weakly binds TRRAP are still fully active in transient transfection reporter assays and the TATA binding protein (TBP) has been reported to directly bind Myc, we sought to determine the effect of TBP on Myc transactivation.

Pathogen Genomics, 2002

Bacterial" Genes-to-Screens" in the Post-Genomic Era Michael J. Pucci, John F. Barrett,... more Bacterial" Genes-to-Screens" in the Post-Genomic Era Michael J. Pucci, John F. Barrett, and Thomas J. Dougherty INTRODUCTION In ... 23. Kotra LP, Vakulenko S. Mobashery S. From genes to sequences to antibiotics: prospects for future developments from microbial genomics. ...

Virus research, 2009

Myxoma virus (MV) is a highly lethal, rabbit-specific poxvirus that induces a disease called myxo... more Myxoma virus (MV) is a highly lethal, rabbit-specific poxvirus that induces a disease called myxomatosis in European rabbits. In an effort to understand the function of predicted immunomodulatory genes we have deleted various viral genes from MV and tested the ability of these knockout viruses to induce lethal myxomatosis. MV encodes a unique 15 kD cytoplasmic protein (M130R) that is expressed late (12h post infection) during infection. M130R is a non-essential gene for MV replication in rabbit, monkey or human cell lines. Construction of a targeted gene knockout virus (vMyx130KO) and infection of susceptible rabbits demonstrate that the M130R knockout virus is attenuated and that loss of M130R expression allows the rabbit host immune system to effectively respond to and control the lethal effects of MV. M130R expression is a bona fide poxviral virulence factor necessary for full and lethal development of myxomatosis.

European Journal of Biochemistry, 1997

The tapeworm Moniezia expansa contains an extremely abundant cytoplasmic lipid-binding protein (L... more The tapeworm Moniezia expansa contains an extremely abundant cytoplasmic lipid-binding protein (LBP). It is a small protein consisting of 66 amino acids with a molecular mass of 7943Ϯ1.5 Da. The amino acid sequence has been established by Edman degradation and confirmed by PCR analysis. The Moniezia LBP shows no sequence similarity with any previously described binding protein, but does show similarity with antigen B from Echinococcus glanulosus and Echinococcus multilocularis and with Taenia crassiceps antigen. The predicted structure for Moniezia LBP shows four helices and a putative tyrosine kinase site on the loop between helix 1 and 2. Each of the four helices has a well defined hydrophobic face. Studies with fluorescent probes suggest a single hydrophobic binding site. Results indicate that the single tryptophan residue in the molecule (Trp41) is involved in ligand binding, and calculation of the Stern-Volmer quenching constant shows that Trp41 is in a relatively hydrophobic environment.

Cheminform, 2010

Conjugates.

Botanical Journal of Scotland, 2002

The Killarney Fern (Trichomanes speciosum) was considered amongst the rarest and most vulnerable ... more The Killarney Fern (Trichomanes speciosum) was considered amongst the rarest and most vulnerable of Europe's plants. Research which fed into the Biodiversity Action Plan and developed alongside it, has forced us to reconsider the level of threat to this species. A hitherto overlooked stage of the life-cycle, the gametophyte, has been shown to be comparatively abundant, genetically diverse, largely threat-free and with the potential over time to regenerate the familiar sporophyte stage. This research also promoted wider public interest which itself generated additional records, such that even the sporophyte is now known at more British sites than at any time previously and the species is accordingly considered ‘recovered’. However, continued legal protection and the need for further research are still recommended.

Nature Immunology, 2004

Myxoma virus, a member of the poxvirus family, causes lethal infection only in rabbits, but the m... more Myxoma virus, a member of the poxvirus family, causes lethal infection only in rabbits, but the mechanism underlying the strict myxoma virus species barrier is not known. Here we show that myxoma virus infection of primary mouse embryo fibroblasts elicited extracellular signal-regulated kinase (Erk) signaling, which was integrated to interferon regulatory factor 3 activation and type I interferon induction. We further show that Erk inactivation or disruption of interferon signaling mediated by the transcription factor STAT1 broke the cellular blockade to myxoma virus multiplication. Moreover, STAT1 deficiency rendered mice highly susceptible to lethal myxoma virus infection. Thus, the Erk-interferon-STAT1 signaling cascade elicited by myxoma virus in nonpermissive primary mouse embryo fibroblasts mediates an innate cellular barrier to poxvirus infection.

ChemInform, 2009

Peptides U 0400 Isolation, Structure, and Antibacterial Activity of Thiazomycin A, a Potent Thiaz... more Peptides U 0400 Isolation, Structure, and Antibacterial Activity of Thiazomycin A, a Potent Thiazolyl Peptide Antibiotic from Amycolatopsis fastidiosa. -(ZHANG, C.; ZINK, D. L.; USHIO, M.; BURGESS, B.; ONISHI, R.; MASUREKAR, P.; BARRETT, J. F.; SINGH*, S. B.; Bioorg.