Abstract
The affinities of ten streptomycin (SM) derivatives were compared to that of tritium labelled dihydro-streptomycin (T-DHS) towards "run off" 70S ribosomal particles from a sensitive E. coli. The in vitro affinities were correlated with the in vivo activities (killing activities). High affinity and activity could only be demonstrated in derivatives with an intact streptidine (SD) moiety. Furthermore an interaction between the streptose branch and the amino group was necessary to obtain high affinity and activity. The highest in vivo activity was found when the amino group was N-mono-methyl substituted. Our results indicate that SM binds to two sites at the 70S particles, one having the character of a cation-exchanger (RNA), the other being presumably a metal ion (Mg2+). The metal ion probably forms a complex with the glucosamine and the streptose branch moieties.
