Molecular Pharmacology, Vol 4, 25-37, Copyright © 1968 by the American Society for Pharmacology and Experimental Therapeutics

Studies of the Binding of Tetracycline to Ribosomes in Vitro

¹ Subdepartment of Chemical Microbiology, Department of Biochemistry, University of Cambridge, Cambridge, England

Ribosomes, isolated from Bacillus megaterium or from rat liver, were found capable of binding considerable quantities of tetracycline. The amount bound depended upon the concentrations of tetracycline and of Mg²⁺ and K⁺ present. The highest level of binding observed was equivalent to about 300 molecules of tetracycline per ribosome.

Binding of the antibiotic was largely reversible, but, using tetracycline-³H of high specific activity, it was possible to detect a low level of irreversible binding, amounting to less than one molecule per ribosome under the conditions used. This binding was observed to take place to both 30 S and 50 S ribosome subunits.

The possible relevance of the binding to inhibition of protein synthesis by tetracycline is discussed.

Note:
ACKNOWLEDGMENTS The author wishes to thank members of the Subdepartment of Chemical Microbiology, in particular Dr. Kenneth McQuillen, for much valuable discussion. Thanks are due to the Medical Research Council for a Scholarship for Training in Research Methods and to Merck Sharp and Dohme for a generous gift of actinomycin.