Interaction of nucleosides and related compounds with nucleic acids as indicated by the change of helix-coil transition temperature.

Streptomycin decreased the polyuridylic acid-dependent incorporation of C'4-labeled phenylalanine into acid-insoluble products in a cell-free system containing ribosomes of streptomycin sensitive E. coli and supernatant of either sensitive or resistant cells. There was no inhibition when the system contained ribosomes of streptomycin resistant E. coli and supernatant of either resistant or sensitive cells. The experiments show that streptomycin interferes with ribosomal function in sensitive bacteria and point to the ribosomes as the site of streptomycin sensitivity. They also show that the genetic locus determining streptomycin sensi tivity is part of a ribosome-specific region of the bacterial chromosome.