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Furth, H. P.; Ackerman, Jerome L.; Becker, J. J.; Lykoudis, Paul S.; Litterst, F. Jochen; Kalvius, Georg Michael; Williams, D. J.; Callen, Earl; Krishna, K. R.; Troup, G. J.; Soldano, B. A.; Sharkey, A. G.; Band, William; Lawden, D. F.; Heading, J.; Baird, D. C.; Sprackling, Michael; Hecht, Eugene; Skaggs, Lester S.; Martin, J. W.; Blackadar, Alfred; Shankland, R. S.; Hösemann, R.; Burkhard, Donald G.; Giordano, Anthony B.; Alley, Charles L.; Kieffer, William F.; Birge, Edward A.; Knight, R. D.; Beyer, George L.; King, G. W.; Ingalls, R.; Debrunner, Peter G.; Brockhurst, Frederick C.; Josephs, Jess J.

doi:10.1007/978-1-4615-6902-2_12

Cited by 3 publications

(4 citation statements)

References 25 publications

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“…This also indicated that SV40 large T did not alter v-Ha-ras expression. p21v-Ha-ras migrated with a slightly slower mobility (see Furth et al, 1982), as clearly seen for the LTts-ras clone 33-4 ras2 ( v-Ha-ras induces reversible growth arrest The growth of pairs of LTts and LTts-ras clones was analysed at the permissive (33°C) and restrictive (39.5°C) temperatures for the temperature-sensitive large T mutant. Preliminary characterization of LTts cells showed that their behaviour was comparable to LT cells at 33°C, in that they were able to grow in FBS-DMEM without 259 CM.…”

Section: Lj-tssvmentioning

confidence: 90%

Ras-mediated cell cycle arrest is altered by nuclear oncogenes to induce Schwann cell transformation.

Ridley¹,

Paterson²,

Noble³

et al. 1988

The EMBO Journal

212

136

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The cellular responses to ras and nuclear oncogenes were investigated in purified populations of rat Schwann cells. v‐Ha‐ras and SV40 large T cooperate to transform Schwann cells, inducing growth in soft agar and allowing proliferation in the absence of added mitogens. Expression of large T alone reduces their growth factor requirements but is insufficient to induce full transformation. In contrast, expression of v‐Ha‐ras leads to proliferation arrest in Schwann cells expressing a temperature‐sensitive mutant of large T at the restrictive temperature. Cells arrest in either the G1 or G2/M phases of the cell cycle, and can re‐enter cell division at the permissive temperature even after prolonged periods at the restrictive conditions. Oncogenic ras proteins also inhibit DNA synthesis when microinjected into Schwann cells. Adenovirus E1a and c‐myc oncogenes behave similarly to SV40 large T. They cooperate with Ha‐ras oncogenes to transform Schwann cells, and prevent ras‐induced growth arrest. Thus nuclear oncogenes fundamentally alter the response of Schwann cells to a ras oncogene from cell cycle arrest to transformation.

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Section: Lj-tssvmentioning

confidence: 90%

Ras-mediated cell cycle arrest is altered by nuclear oncogenes to induce Schwann cell transformation.

Ridley¹,

Paterson²,

Noble³

et al. 1988

The EMBO Journal

212

136

View full text Add to dashboard Cite

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“…1. Nine mAbs (13,14,17,18,20,25, 31A, 31B and Ha784) did not bind to the synthesized peptides at all (data not shown). Two possible explanations for their lack of reactivity are that their epitopes are longer than 8 amino acid residues and that they recognize and that they recognize only the native conformations of the ras proteins.…”

Section: Resultsmentioning

confidence: 92%

“…Monoclonal antibodies as tools for detection and the functional analyses of ras proteins Several investigators have studied ras protein function by microinjecting cells with neutralizing anti-rus mAbs (9)(10)(11)(12)(13). For example, the mAb Y 13-256 interacts with the side-chains of residues Glu", Ser6', Ala66, Met67, Gin" and Arg73 (24) in ras protein and can inhibit both its activity (10) and its interaction with GAP (9,11,13). On the other hand, mAb Y13-238 inhibits neither GAP activity (1 2) nor ras activity (25); mAb Y 13-259 specifically blocks the serum-induced mitogenic response of certain cells in culture and inhibited morphologic transformation induced by mutant rus proteins (26).…”

Section: Discussionmentioning

confidence: 99%

Epitopic characterization of the human wild‐type and mutant ras proteins using membrane‐bound peptides

Wang

Carney

Laursen

1997

The Journal of Peptide Research

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Overlapping octapeptides encompassing the entire sequences of the human oncogene products Ha‐ras, K‐ras and N‐ras protein were synthesized as spots on polypropylene membrane sheets. The binding of anti‐row protein monoclonal antibodies (mAbs) to the membrane‐bound peptides was assessed using an enzyme‐linked immunosorbent assay. Epitopes of 10 of 18 mAbs to the human ras proteins were mapped and identified by this procedure. The epitopes of nine of the mAbs are within residues 28‐39 in the constant domain common to the three ras proteins, whereas the epitope of the tenth (mAb 21) spans residues 136‐144 in Ha‐ras. The minimal lengths of epitopes of all ten of the mAbs were further precisely mapped using peptides of varying length, and the tolerance for mAb binding of mutated epitopes was determined by systematically replacing each residue in the epitope with each of the 20 common amino acids. The results show that most of these mAbs have essentially the same binding specificity, namely for the sequence YDPT (residues 32–35) or for slightly longer sequences containing these residues. This site is in the switch 1 region (residues 32‐38) in the ras effector loop, indicating that some of the same residues important for the interaction of ras with other proteins (GTPase‐activating protein, neurofibromin or raf) are highly antigenic. In addition, we investigated epitopes and specificity of five mAbs against the activated human ras proteins by the same procedure. The information gained from this study should be useful both for study of the complicated functions of ras proteins and for clinical detection of ras oncogenes in human tumor cells.

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“…This figure is converted to mass of enzyme by multiplying by the M,, which is approximately 42000 [60]. Then a trapping mechanism of resistance would require a rate of p-lactamase synthesis of 5.03 pg enzyme min-' (mg dry cells)-'.…”

Section: Discrimination Between Putative Trapping and Hydrolytic Resimentioning

confidence: 99%

Permeability to cefsulodin of the outer membrane of Pseudomonas aeruginosa and discrimination between β‐lactamase‐mediated trapping and hydrolysis as mechanisms of resistance

Hewinson

Cartwright

Slack

et al. 1989

European Journal of Biochemistry

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A pair of strains of Pseudomonas aeruginosa (3-Pre : cefsulodin-sensitive, inducible /?-lactamase ; and 3-Post: cefsulodin-resistant, elevated fl-lactamase, derived from 3-Pre by subculture in the presence of cefsulodin) were taken as representative of the class of bacteria resistant to third-generation cephalosporins due to elevated synthesis of the normally inducible, chromosomally encoded j-lactamase. These two strains were used to differentiate between 'trapping' and 'hydrolytic' mechanisms of cefsulodin resistance by (a) measuring the outer-membrane permeabilities to cefsulodin, (b) measuring the kinetics of cefsulodin hydrolysis and the stoichiometry of cefsulodin trapping by the periplasmic b-lactamase, and (c) comparing the predictions of the trapping and hydrolysis hypotheses with the minimum inhibitory concentrations (MIC) of cefsulodin. The MIC of cefsulodin for strains 3-Pre and 3-Post were 2.35 pM (1.25 pg ml-') and 37.6 pM (20.0 pg ml-') respectively. The permeability parameter for cefsulodin of the outer membrane of the resistant strain was 0.0034 cm3 min-' mg dry mass-', so the flux of cefsulodin across its outer membrane at the MIC was calculated to be 0.120 nmol min-' mg dry mass-'.Hydrolysis of cefsulodin by the p-lactamase in the periplasm occurred at a rate of 0.1 18 nmol min-' mg dry mass-' which can thus account for resistance by matching the above rate of inflow. Trapping by the P-lactamase, even with a 1 : 1 stoichiometry, would require the enzyme to be synthesized at 5.0 pg protein min-' mg dry mass-' or about 40% of the dry mass/generation. We conclude that hydrolysis, but not trapping, adequately explains the resistance to cefsulodin in P. aeruginosa 3-Post. A similar calculation for latamoxef resistance, using data taken from the literature. led to the same conclusion.Resistance to third-generation cephalosporins [l] in gramnegative bacteria possessing inducible class-C [2] P-lactamases can occur by mutation to continuous elevated synthesis of the enzyme [3 -91. The mechanism of this form of resistance has been the subject of much debate, because in general these p-lactamases possess low or undetectable hydrolytic activity against such compounds [8, proposed that the mechanism of resistance was one of trapping (i. Abbreviations. CDM, chemically defined medium; MIC, minimum inhibitory concentration.Enzymes. fi-Lactamase (EC 3.5.2.6); lysozyme (EC 3.2.1.17); ribonuclease A (EC 3.1.27.5).In order to test the hypothesis that a low hydrolytic activity is sufficient to explain the antibiotic resistance, three sets of measurements need to be made [19-221. The first is the MIC (minimum inhibitory concentration) of a third-generation cephalosporin for a ,U-lactamase-inducible strain, and for an otherwise isogenic resistant mutant synthesizing an elevated amount of fl-lactamase. Secondly the kinetics of hydrolysis and the stoichiometry of trapping of the compound by the j-lactamase in each of the above two strains must be measured. Thirdly, the outer membrane permeability of each of the above ...

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M

Cited by 3 publications

References 25 publications

Ras-mediated cell cycle arrest is altered by nuclear oncogenes to induce Schwann cell transformation.

Ras-mediated cell cycle arrest is altered by nuclear oncogenes to induce Schwann cell transformation.

Epitopic characterization of the human wild‐type and mutant ras proteins using membrane‐bound peptides

Permeability to cefsulodin of the outer membrane of Pseudomonas aeruginosa and discrimination between β‐lactamase‐mediated trapping and hydrolysis as mechanisms of resistance

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