Binding of [3H]tetrahydroleucomycin A3 to Escherichia coli ribosomes and the effect of 3"-O-acyl derivatives of leucomycins on the binding.

The analysis of [3H]tetrahydroleucomycin A3 binding to Escherichia coli ribosomes are described. The dissociation constant for tetrahydroleucomycin A3 binding to ribosomes was 1.15 x 10(-8) M. One molecule of tetrahydroleucomycin A3 was bound to each 70 S ribosome (50 S subunit) as reported with erythromycin. The effect of leucomycins and their 3"-O-acyl derivatives on [3H]tetrahydroleucomycin A3 binding to ribosomes was examined. In general, 3"-O-acyl derivatives of leucomycins exhibited stronger antimicrobial activity against Gram-positive bacteria and weaker (or equivalent) activity against E. coli than their mother compounds. However, the affinities to ribosomes were approximately equivalent to those of the mother compounds, suggesting that Gram-positive bacterial cells are more permeable to 3"-O-acyl derivatives than to the mother compounds.