1977 Volume 30 Issue 2 Pages 132-140
Minosaminomycin is structurally related to kasugamycin and inhibits protein synthesis in mycobacteria. It also inhibits phage f2 RNA-directed protein synthesis in a cell-free system of Escherichia coliby 50% at 2×10-7M. It is 100-times more potent than kasugamycin in this system. At 10-7M minosaminomycin inhibits EF-T dependent binding of aminoacyl-tRNA to ribosomes by 50%. This effect is markedly diminished if minosaminomycin is added to the assay say system after a brief incubation of ribosomes with mRNA. Like kasugamycin, minosa- minomycin preferentially inhibits the initiation of protein synthesis directed by phage f2 RNA in vitroand does not cause miscoding. Ribosomes from kasugamycin-resistant mutants Ksg A and Ksg C were as sensitive to minosaminomycin as those from each parent strain. In spite of the strong inhibitory activity of minosaminomycin manifested in cell-free systems ofE. coli, this compound inhibits the growth of the organism itself only slightly. This discrepancy could be ascribed to impermeability, asE. colicells with modified permeability show greater sensitivity sitivity to minosaminomycin. There is no indication that the antibiotic is inactivated inE. coli cells. On the basis of these results, the structural features of these antibiotics essential for interaction with ribosomes and for permeability into the cells are discussed.
