Tadatoshi Kinoshita

Inhibition by kasugamycin of initiation complex formation on 30S ribosomes

Summary The mechanism of action of kasugamycin, an aminoglycosidic antibiotic, has been comparatively studied with those of other aminoglycosides. The initiation complex formation on 30S ribosomes is inhibited by kasugamycin but not by streptomycin, kanamycin or gentamicin, although the binding of fMet-tRNA to 70S ribosomes is inhibited both by kasugamycin and by streptomycin. The 70S complex formation is inhibited by kasugamycin but not by streptomycin when GTP is replaced by GMPPCP. The results indicate that the 30S initiation complex formation is a primary site of kasugamycin action but the other aminoglycosides interfere with a certain process after forming the complex.

Association of fusidic acid sensitivity with G factor in a protein-synthesizing system

Abstract It was observed that fusidic acid and related steroidal antibiotics inhibit protein synthesis in the in vivo and in vitro bacterial systems ( Yamaki, 1965 , Harvey et al., 1966 , Tanaka et al., 1967 ). In an E. coli system, they inhibit ribosome-dependent GTPase reaction with G factor of transfer enzymes, and the grade of inhibition is parallel to that of polypeptide synthesis. It was further suggested by the experiments, using puromycin reaction, that the antibiotics inhibit translocation of peptidyl-tRNA on the ribosomes ( Tanaka et al., 1968 ). Fusidic acid inhibits GTPase activity, observed in combination of the ribosomes and G factor. The localization of fusidic acid sensitivity was further studied with respect to the ribosomes and G factor of drug-sensitive E. coli cells and those of resistant cells. The results are presented in this communication. It was demonstrated that the fusidic acid sensitivity is associated with G factor, but not with the ribosomes.

Inhibition by thiopeptin of ribosomal functions associated with T and G factors

Abstract Thiopeptin, a new antibiotic, inhibits T factor-dependent binding of phe-tRNA to ribosomes, without appreciable inhibition of GTP-Tu-phe-tRNA complex formation. GTP hydrolysis coupled with the phe-tRNA binding is affected by the antibiotic. It also interferes with fusidic acid-sensitive hydrolysis of GTP caused by interaction with G factor and ribosomes. Siomycin acts similarly.

Complex formation of fusidic acid with G factor, ribosome and guanosine nucleotide

Abstract Fusidic acid binds with G factor. The binding is much stimulated by ribosomes and GTP. Formation of fusidic acid-G factor-GDP-ribosome complex is demonstrated by equilibrium dialysis and ultracentrifugal separation methods. Measurements of binding at equilibrium indicate a stoichiometric combination of the four substances in a molar ratio of 1:1:1:1, provided that the ribosomes employed are half active in this function. The association constant of fusidic acid is 2×106 or 6×106 M−1. Less binding of the antibiotic is observed when fusidic acid-resistant G factor is used.

Chromosomal location of a fusidic acid resistant marker in escherichia coli

Abstract A mutation in Escherichia coli to resistance to fusidic acid, a steroidal antibiotic, alters G factor. Fusidic acid resistance ( fus ) is located at minute 64, about 0.2 min. from the strA gene, and may lie between the strA and malA loci.

Selective inhibition of initiation of globin synthesis by phenomycin

Summary It has been demonstrated in a rabbit reticulocyte system that phenomycin selectively blocks the initiation of globin synthesis. The N-terminal incorporation of valine or methionine is more markedly inhibited by the antibiotic than the total incorporation. The 80S initiation complex is accumulated in the presence of phenomycin. The initial dipeptide formation (Met-Val) is significantly affected by the antibiotic.