Open AccessThe Inhibition Pattern of Antibiotics on the Extent and Accuracy of tRNA Binding to the Ribosome, and Their Effect on the Subsequent Steps in Chain Elongation
Author(s) -
WURMBACH Peter,
NIERHAUS Knud H.
Publication year - 1983
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1983.tb07109.x
Subject(s) - viomycin , a site , binding site , ribosome , p site , transfer rna , neomycin , streptomycin , biochemistry , aminoglycoside , biology , active site , chemistry , stereochemistry , antibiotics , rna , enzyme , gene
Ac[ 14 C]Phe‐tRNA (cognate) and Ac[ 3 H]Leu‐tRNA (miscognate) were bound as competing peptidyl‐tRNA analogues to tightly coupled ribosomes programmed with poly(U). The test system allows the determination of the accuracy of tRNA selection at the A and P site, as well as the measurement of the peptidyltransferase and translocation reactions in the presence of various antibiotics. The following results were obtained.1 Cognate tRNA could be bound to either the A or P site with nearly 10% specificity. In contrast, miscognate tRNA could be exclusively bound to the P site but poorly to the A site. 2 The accuracy of tRNA selection (extent of binding) was sixfold higher at the A site than at the P site. 3 The extent of A site binding for both cognate and miscognate tRNA was severely inhibited by viomycin, tetracycline and neomycin, and to a lesser extent by streptomycin. No inhibition of binding at the P site was found with all antibiotics tested. This finding, and that of the preceding point, is taken as evidence that acetylated aminoacyl‐tRNA (an analogue for a peptidyl‐tRNA) has direct access to the P site and does not reach this site via a transient A site binding. 4 In addition to the known effects of streptomycin and neomycin on tRNA selection at the A site, viomycin was found to enhance drastically the error fraction at this site. 5 The peptidyltransferase is inhibited by the drugs in the following order: chloramphenicol > viomycin, neomycin > streptomycin. Equivalent results were found with cognate and miscognate tRNA. The translocation reaction was severely inhibited by viomycin and neomycin and to a lesser extent by streptomycin. 6 A striking correspondence was found between the error‐inducing capacity (distortion of codon‐anticodon interaction at the A site) and the inhibition of the translocation reaction by various drugs. This finding suggests that codon‐anticodon interaction at the ribosomal A site is an important if not essential prerequisite for the translocation reaction.