ROLE OF THE C(1) TRIOL GROUP IN BICYCLOMYCIN - SYNTHESIS AND BIOCHEMICAL AND BIOLOGICAL PROPERTIES

Bicyclomycin (1) is a commercial antibiotic whose primary site of acti on in Escherichia coli is the essential cellular protein transcription termination factor rho. The bicyclomycin binding domain in rho is unk nown; however, enzyme irreversible inactivators that modify rho upon a ctivation may identify the site. In this study, we investigated the im portance for rho binding of the C(1) triol group in 1. Twelve bicyclom ycin derivatives were prepared, and the C(1) triol group was modified at the C(1'), the C(2'), and the C(3') sites. The compounds were evalu ated by rho-dependent ATPase and transcription termination assays and their antimicrobial activities assessed using a filter disc assay. Bic yclomycin inhibited both rho-dependent ATPase (I-50 = 60 mu M) and rho -dependent transcription termination (I-50 similar to 5 mu M) processe s and had a minimum inhibitory concentration value of 0.25 mg/mL again st E. coli W3350 cells. None of the 12 C(1) triol bicyclomycin derivat ives significantly inhibited rho-dependent ATPase (I-50 > 400 mu M) an d transcription termination (I-50 > 100 mu M) activities or exhibited antibiotic activity at a 32 mg/mL concentration. These results indicat ed that there was a strong molecular complement between the C(1) triol group and its rho binding site. We concluded that the C(1) triol grou p in 1 is a critical structural element necessary for drug binding to rho and that an enzyme irreversible inactivating unit placed at this s ite would prohibit the bicyclomycin derivative from efficiently bindin g to rho.