Protorubradirin is an antibiotic that can be isolated from the non-pigmented Streptomyces achromogenes var. rubradiris alongside Rubradirin. It exhibits inhibitory activity against HIV reverse transcriptase. In vitro studies show that Protorubradirin also inhibits strains of Staphylococcus aureus and Streptococcus. In infected mice, subcutaneous administration of Protorubradirin demonstrates in vivo efficacy against antibiotic-resistant Staphylococcus aureus strains. However, oral administration may significantly reduce its activity compared to Rubradirin, possibly due to its C-nitroso sugar decomposing more rapidly in acidic gastric conditions.