194852-24-9Relevant academic research and scientific papers
Design, syntheses, and evaluations of bicyclomycin-based rho inactivators
Cho, Hangjin,Park, Hyeung-Geun,Zhang, Xiangdong,Riba, Isabel,Gaskell, Simon J.,Widger, William R.,Kohn, Harold
, p. 5432 - 5440 (2007/10/03)
The commercial antibiotic bicyclomycin (1) has been shown to target the essential transcriptional termination factor rho in Escherichia coli. Little is known, however, about the bicyclomycin binding site in rho. A recent structure-activity relationship study permitted us to design modified bicyclomycins that may irreversibly inactivate rho. The four compounds selected were C(5a)-(4-azidoanilino)dihydrobicyclomycin (3), C(5a)-(3- formylanilino)dihydrobicyclomycin (4), C(5)-norbicyclomycin C(5)-O-(4- azidobenzoate) (5), and C(5)-norbicyclomycin C(5)-O-(3-formylbenzoate) (6). In each of these compounds the inactivating unit was placed at the C(5)- C(5a) site in bicyclomycin. In compounds 3 and 5 an aryl azide moiety was used as a photoaffinity label whereas in 4 and 6 an aryl aldehyde group was employed as a reductive amination probe. The synthesis and spectral properties of 3-6 are described. Chemical studies demonstrated that 3 and 4 were stable in D2O and CD3OD (room temperature, 7 d), while 5 and 6 underwent significant change within 1 d. Biochemical investigations showed that 3 and 4 retained appreciable inhibitory activities in rho-dependent ATPase and transcription termination assays. In the ATPase assay, I50 values for 1, 3, and 4 were 60, 135, and 70 μM, respectively. Correspondingly, the I50 values for 5 and 6 were >400 and 225 μM, respectively. In the transcription termination assay, compounds 1, 3, and 4 all prevented (≤97%) the production of rho-dependent transcripts at 40 μM, whereas little (≤15%) inhibition of transcription termination was observed for 5 and 6 at this concentration. Antimicrobial evaluation of 3-6 showed that none of the four compounds exhibited antibiotic activity at 32 mg/mL or less against W3350 E. coli. The combined chemical and biochemical studies led to our further evaluation of 3 and 4. Photochemical irradiation (254 nm) of 3 in the presence of rho led to a 29-32% loss of rho ATPase activity. Attempts to confirm the irreversible adduction of 3 to rho by electrospray mass spectrometry were unsuccessful. No higher molecular weight adducts were detected. Incubation of rho with 4 at room temperature (4 h) followed by the addition of NaBH4 led to significant losses (>62%) of rho ATPase activity. Analyses of the 4-rho modified adduct showed appreciable levels of adduction (~40%). Mass spectrometric analyses indicated a molecular weight for the adduct of approximately 47 410, consistent with a modification of a rho lysine residue, by 4. Compound 4 was selected for additional studies.
