Tetracycline can inhibit tRNA binding to the ribosomal P site as well as to the A site.
A and P sites of Escherichia coli ribosomes were titrated with AcPhe-tRNAPhe, in the absence or presence of tetracycline. The P-site location of the bound AcPhe-tRNA was assessed by means of a quantitative puromycin reaction. The results demonstrate that, in agreement with the generally held view, tetracycline exclusively inhibits the A-site binding, if the statistical number of bound acyl-tRNA molecules per ribosome does not exceed about 0.5. However, above this value the P site becomes sensitive to tetracycline as well. It follows that the tightly coupled 70S ribosomes used in functional studies appear to be functionally heterogeneous, i.e. those P sites which cannot be affected by tetracycline are preferentially occupied by AcPhe-tRNA, whereas higher concentrations of this tRNA species are required to fill tetracycline-sensitive P sites. Furthermore, the results imply that under tRNA saturation conditions the tetracycline inhibition cannot be used as an indicator for the site location of bound tRNA.
D000495:Allosteric Site; D001665:Binding Sites / Q000187:drug effects; D001667:Binding, Competitive; D008954:Models, Biological; D011691:Puromycin / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D013752:Tetracycline / Q000494:pharmacology*
D012346:RNA, Transfer, Amino Acyl; C006383:tRNA, N-acetylphenylalanine-; D011691:Puromycin; D012343:RNA, Transfer; D013752:Tetracycline