Interaction between the Erythromycin and Chloramphenicol Binding Sites on the Escherichia Coli Ribosome

Richard Langlois, Charles R. Cantor, Robert Vince, Sidney Pestka

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


The effects of chloramphenicol on the binding kinetics of a fluorescein isothiocyanate derivative of 9(S)-erythromycylamine with 70S and 50S ribosomes have been studied by direct fluorimetric measurements. While chloramphenicol had little effect on the second-order 70S binding rate of the erythromycin analogue, it substantially reduced the dissociation rate of the fluorescent antibiotic-70S ribosome complex. This could be explained by simultaneous binding of both antibiotics to the 70S ribosome. The kinetic results suggest that chloramphenicol-saturated 70S particles bind the erythromycin analogue four times stronger and this was confirmed by direct binding studies. In addition, chloramphenicol causes a twofold increase in the intrinsic fluorescence of the 70S-bound analogue. This increase in fluorescence was used to study the kinetics of chloramphenicol binding to 70S ribosomes containing the fluorescent derivative. The fluorescence change followed first-order kinetics, suggesting that chloramphenicol induces a conformational change in the 70S particle. This could explain both its effect on erythromycin binding and on the fluorescence of bound analogue. Less detailed results with the 50S particle indicate a qualitatively similar picture of erythromycin-chloramphenicol interactions.

Original languageEnglish (US)
Pages (from-to)2349-2356
Number of pages8
Issue number11
StatePublished - May 1 1977
Externally publishedYes


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