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Biomedical subjects

G Painter

Publications and source records attributed to G Painter.

16 recordsLinked to original sources
PubMed2002

Identification of ARAP3, a novel PI3K effector regulating both Arf and Rho GTPases, by selective capture on phosphoinositide affinity matrices.

We show that matrices carrying the tethered homologs of natural phosphoinositides can be used to capture and display multiple phosphoinositide binding proteins in cell and tissue extracts. We present the mass spectrometric identification of over 20 proteins isolated by this method, mostly from leukocyte extracts: they include known and novel proteins with established phosphoinositide binding domains and also known proteins with surprising and unusual phosphoinositide binding properties. One of the novel PtdIns(3,4,5)P3 binding proteins, ARAP3, has an unusual domain structure, including five predicted PH domains. We show that it is a specific PtdIns(3,4,5)P3/PtdIns(3,4)P2-stimulated Arf6 GAP both in vitro and in vivo, and both its Arf GAP and Rho GAP domains cooperate in mediating PI3K-dependent rearrangements in the cell cytoskeleton and cell shape.

ADP-Ribosylation Factor 6↗
PubMed1998

The stress-activated phosphatidylinositol 3-phosphate 5-kinase Fab1p is essential for vacuole function in S. cerevisiae.

Polyphosphoinositides have many roles in cell signalling and vesicle trafficking [1-3]. Phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2), a recently discovered PIP2 isomer, is ubiquitous in eukaryotic cells and rapidly accumulates in hyperosmotically stressed yeast. PI(3,5)P2 is synthesised from PI(3)P in both yeast and mammalian cells [4,5]. A search of the Saccharomyces cerevisiae genome database identified FAB1, a gene encoding a PIP kinase homologue and potential PI(3)P 5-kinase. Fab1p shows PI(3)P 5-kinase activity both in vivo and in vitro. A yeast strain in which FAB1 had been deleted was unable to synthesise PI(3,5)P2, either in the presence or absence of osmotic shock. A loss of PI(3,5)P2 was observed also in a temperature-sensitive FAB1 strain at the non-permissive temperature. A recombinant glutathione-S-transferase (GST)-Fab1p fusion protein was shown to have selective PI(3)P 5-kinase activity in vitro. Thus, we have demonstrated that Fab1p is a PI(3)P-specific 5-kinase and represents a third class of PIP kinase activity, which we have termed type III. Deletion of the FAB1 gene produces a loss of vacuolar morphology [6]; it is therefore concluded that PI(3,5)P2, the lipid product of Fab1p, is required for normal vacuolar function.

Mutagenesis↗
PubMed1996

In vitro antiviral activity of 141W94 (VX-478) in combination with other antiretroviral agents.

141W94 (VX-478) is a novel HIV-1 protease inhibitor with an IC50 of 0.08 microM against HIV-1 (strain IIIB) and a mean IC50 of 0.012 microM against six HIV clinical isolates. 141W94 was synergistic on the basis of isobologram analysis with each of the following reverse transcriptase inhibitors: AZT, 935U83, 524W91, 1592U89 and ddl, 141W94 was also synergistic with saquinavir and additive with either indinavir or ritonavir. Resistance to 141W94 has been reported in vitro passage experiments. The binding of 141W94 to human alpha 1-acid glycoprotein was relatively weak (Kd = 4 microM) and the off-rate for the drug is very fast (> or = 100 s-1). Only a 2-fold reduction of in vitro antiviral activity was observed in the presence of 45% human plasma. No serious drug associated adverse experiences were reported in a Phase I placebo-controlled, single-dose escalation, pharmacokinetic and safety study. The average concentration of 141W94 at 8 and 12 h after single doses of 900 and 1200 mg, respectively, was in excess of 10 times the IC50. As 141W94 is synergistic with a variety of anti-HIV-1 agents and exhibits a unique cross resistance profile compared to other protease inhibitors, 141W94 is considered a good candidate for combination therapy.

Carbamates↗
PubMed1993

The 5'-triphosphates of the (-) and (+) enantiomers of cis-5-fluoro-1-[2-(hydroxymethyl)-1,3-oxathiolane-5-yl]cytosine equally inhibit human immunodeficiency virus type 1 reverse transcriptase.

The (-) enantiomer of cis-5-fluoro-1-[2-(hydroxymethyl)-1,3-oxathiolane-5-yl]cytosine is a potent inhibitor of human immunodeficiency virus type 1 in vitro. The 5'-triphosphates of the (-) and (+) enantiomers equally inhibited the production of full-length minus-strand DNA in an endogenous reverse transcriptase reaction, each competitively inhibited DNA synthesis, and each was used as a chain-terminating substrate.

Antiviral Agents↗
PubMed1991

Substrate inhibition of the human immunodeficiency virus type 1 reverse transcriptase.

Substrate inhibition was observed with the heterodimeric (p66/p51) and the homodimeric (p66/p66, p51/p51) forms of human immunodeficiency virus type 1 reverse transcriptase (RNA-dependent DNA polymerase, EC 2.7.7.49). An apparent Ki value of 195 +/- 37 microM was determined for dTTP using the bacterial cloned and expressed heterodimer. Similar values were obtained with the homodimeric and the virus-encoded enzymes. When poly-(rC).p(dG)10 was used as template-primer, dGTP exhibited substrate inhibition with an apparent Ki value of 189 +/- 32 microM. Substrate inhibition was not observed with dTTP when DNA.DNA template-primers were used. Hill coefficients for substrate binding determined in the presence of saturating concentrations of template-primer were equal to 1.0, suggesting that substrate inhibition of the heterodimer is not the result of an allosteric mechanism involving the p51 subunit. Furthermore, UV crosslinking experiments with [gamma-32P]dTTP showed crosslinking only to the p66 subunit. Substrate inhibition was not as pronounced with other retroviral reverse transcriptases as it was with human immunodeficiency type 1 reverse transcriptase.

Adenosine Triphosphate↗
PubMed1990

The conservative management of choroidal melanoma.

The results of 32 choroidal melanomas managed by observation, Iodine-125 scleral plaques and local surgical excision are presented. Initially, 12 patients were managed by observation, and of these three continued to be managed by observation alone. Fifteen patients were managed with Iodine-125 scleral plaques and followed for an average of 15 months. The tumour regressed in 11, remained the same in three, and recurred in one case. The final visual acuity remained within two Snellen lines of that recorded preoperatively in 10 patients. Fourteen patients underwent local excision with an average follow-up of 31 months. These cases, in general, had larger tumours. The final visual acuity was within two Snellen lines of the preoperative vision in four patients. Five eyes required enucleation at a later date. Four of the five enucleations occurred earlier in the series. The management of choroidal melanoma remains controversial. Various methods of conservative treatment are described and the indications for conservative management by observation, scleral plaque and local excision are discussed.

Adult↗
PubMed1989

Postural drainage in the management of postoperative hyphaema.

We describe the technique of postural drainage of hyphaemas following trabeculectomy alone or when combined with lens extraction and intraocular lens implantation. This technique helps avoid surgical intervention and seems to have no short-term deleterious effect on bleb function.

Cataract Extraction↗
PubMed1984

The biosynthesis of gram-negative endotoxin. Formation of lipid A disaccharides from monosaccharide precursors in extracts of Escherichia coli.

We have discovered an enzyme in the cytosol of Escherichia coli that generates lipid A disaccharides from monosaccharide precursors by the following route: 2,3-diacyl-GlcN-1-P + UDP-2,3-diacyl-GlcN---- 2,3-diacyl-GlcN (beta, 1----6) 2,3-diacyl-GlcN-1-P + UDP. Previous studies from our laboratory have documented the presence in vivo of the precursors 2,3-diacylglucosamine 1-phosphate (2,3-diacyl-GlcN-1-P) (lipid X of E. coli) and UDP-2,3-diacylglucosamine (UDP-2,3-diacyl-GlcN) (Bulawa, C.E., and Raetz, C.R.H.J. Biol. Chem. 259, 4846-4851). Both substrates are novel glucosamine-derived phospholipids, acylated with beta-hydroxymyristoyl moieties, and they accumulate in E. coli mutants defective in the pgsB gene. Synthetic ADP-, GDP-, and CDP-2,3-diacylglucosamines are inefficient substrates compared to the naturally occurring UDP derivative. The free-acid form of the tetraacyldisaccharide 1-phosphate product (C68H129N2O20P) that is generated in vitro has Mr = 1325.74 as judged by fast atom bombardment mass spectrometry. Mild acid hydrolysis (0.1 M HCl for 30 min at 100 degrees C) liberates greater than 95% of the phosphate moiety as Pi. Detailed analysis by 1H and 13C NMR spectroscopy confirms the presence of a phosphate residue at position 1 of the disaccharide, an alpha-anomeric configuration at the reducing end, and a beta, 1----6 linkage between the two glucosamines. Importantly the disaccharide 1-phosphate synthase is missing in extracts of E. coli strains harboring the pgsB1 mutation, consistent with the massive accumulation of 2,3-diacyl-GlcN-1-P and UDP-2,3-diacyl-GlcN in vivo. The enzymatic reaction reported here represents a major biosynthetic route for the formation of lipid A disaccharides in E. coli and other Gram-negative bacteria. An in vitro system for the biosynthesis of lipid A disaccharides has not been described previously.

Disaccharides↗
PubMed1983

The solvent polarity dependent conformational equilibrium of the carboxylic ionophore narasin: a proton NMR study.

Two dimensional homonuclear (1H-1H) chemical shift correlation, double resonance and nuclear Overhauser effect difference spectroscopy were used to determine spectral parameters of narasin acid in different solvents approximating the range of polarities encountered within a biological membrane. The observed chemical shift and coupling constant changes were consistent with a polarity mediated shift between two conformational states, with the major conformational adjustments occurring in two specific backbone regions of the molecule previously described as "hinges" (1,2). Evidence suggests that the conformational equilibrium is not only mediated by solvent polarity but may in part be determined by the intrinsic propensity of narasin to form inclusion complexes with H+.

Chemical Phenomena↗
PubMedDate not supplied

Efficacy of topical acyclovir monophosphate, acyclovir, or penciclovir in orofacial HSV-1 infections of mice and genital HSV-2 infections of guinea pigs.

The purpose of these studies was to compare the efficacy of acyclovir monophosphate (ACVMP), acyclovir (ACV), or penciclovir (PCV) against HSV-1 in an orofacial infection of mice and against ACV sensitive and resistant genital HSV-2 infections of guinea pigs. Treatment was initiated 24, 48, or 72 hours post inoculation with 5% ACVMP, 5% ACV (Zovirax) or 1% PCV (Denavir). In all experiments, similar efficacy was obtained for ACVMP and ACV, whereas PCV was considerably less effective.

Acyclovir↗