Streptogramins-inactivating activity in three producer streptomycetes

The mechanism of self-resistance in three streptogramins-producing streptomycetes was analysed. The three organisms had ribosomes which were sensitive both to A- and B-components of the streptogramin complex. However, cell-free extracts of these producers showed streptogramins-inactivating activity which was independent on the addition of exogenous cofactors (S-adenosylmethionine, ATP or acetyl coenzyme A). The activity was retained by the extracts after dialysis and inactivated by boiling, indicating the presence of enzymatic activity. The inactivating activity was found throughout the growth cycle of the organisms indicating a constitutive nature.