Resistance to thiostrepton, siomycin, and sporangiomycin in actinomycetes that produce them.

The antibiotics thiostrepton, siomycin, and sporangiomycin are closely related both in structure and in mode of action. Actinomycetes which produce this group of compounds possess ribonucleic acid-pentose methylases, which act upon 23S ribosomal ribonucleic acid and render ribosomes resistant to the action of these antibiotics. This is achieved via the formation of a single residue of 2'-O-methyladenosine per ribosome.