Tomoya Kamiya

Potentiation of 5-Fluorouracil, Chromomycin A3, and Bleomycin by Amphotericin B or Polymyxin B in Transformed Fibroblastic Cells

By using cultured, transformed fibroblastic cells, antitumor agents including cytosine arabinoside, thio-tepa, nitrogen mustard N-oxide, mitomycin C, chromomycin A3, 5-fluorouracil, daunomycin, vinblastine, vincristine, and bleomycin A2 were screened for the potentiation of their activity by amphotericin B or polymyxin B. Among them, the action of 5-fluorouracil and chromomycin A3 on ribonucleic acid synthesis was potentiated in their action by amphotericin B, not by polymyxin B. Bleomycin A2 was potentiated in its action on deoxyribonucleic acid and ribonucleic acid synthesis only by polymyxin B.

A mutant of Escherichia coli blocked in peptide elongation: Altered elongation factor Ts

Abstract Among our transfer RNA-dependent growth mutants, one, HAK88, was found that carries an altered elongation factor Ts. The activity of mutant EFTs to bind GDP to EFTu, or to form the ternary complex (aminoacyl-tRNA-EFTu-GTP) is thermolabile. The effect of magnesium on the formation of EFTu-GDP from the EFTu-EFTs complex of HAK8 shows that a four to fivefold increase of the duplex formation occurs when the magnesium concentration is increased from 10−6 m to 10−2 m at 0 °C and at 41 °C. However, at higher temperatures, formation of the binary EFTu-GDP from the EFTu-EFTs complex of HAK88 is depressed, even at 10−3 m to 10−2 m -magnesium. The binding of GDP to the wild-type or mutant EFTu-EFTs complex at 0 °C and 42 °C indicates that the formation of EFTu-GDP is inhibited at 42 °C only when mutant complex is used for the assay. Binding of GTP to complete bacteriophage Qβ replicase (which is known to contain EFTs) formed in phage-infected HAK88 is also inhibited at 42 °C.