Open AccessDual Interference of Hygromycin B with Ribosomal Translocation and with Aminoacyl‐tRNA Recognition
Author(s) -
CABAÑAS Maria Jesús,
VÁZQUEZ David,
MODOLELL Juan
Publication year - 1978
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1978.tb12347.x
Subject(s) - ribosome , puromycin , peptidyl transferase , p site , transfer rna , gtp' , ribosomal rna , biochemistry , a site , protein biosynthesis , chemistry , hygromycin b , chromosomal translocation , biology , microbiology and biotechnology , binding site , enzyme , rna , mutant , gene
In Escherichia coli cell‐free systems, the aminboglycoside antibiotic hygromycin B inhibits (80%) the elogation‐factor‐(EF)G‐plus‐GTP‐dependent reaction of either AcPhe‐tRNA or natural peptideyl‐tRNA with puromycin. The antibiotic does not substantially affect the poly(uridylic acid)‐directed, EF‐Tu‐plus‐GTP‐dependent binding of Phe‐tRNA to ribosomes or the reaction of donor‐site‐bound AcPhe‐tRNA with puromycine. Moreover, the nascnet peptide chains of either purified endogenous E. coli polysomes or poly(uridylic acid)‐programmed ribosomes, blocked by hygromycin B during polypeptide synthesis, react slowly with puromycin while the chains of uninhibited polysomes or tetracycline‐blocked ribosomes react very rapidly. These results indicate that hygromyckin B temporaily retains peptidely‐tRNA in the ribosomal acceptor site and, consequently, that the inhibition of polypeptide chain elongation by the antibiotic is, at least in part, due to the impairment of ribosomal translocation. Hygromycin B at concentrations strongly inhibitory for translocation (80 μM) does not affect the EF‐G‐plus‐ribosome‐dependent GTP hydrolysis, the formation of the GDP · EF‐G · ribosome · fusidic‐acid complex or the non‐enzyme binding of AcPhe‐tRNA to the ribosomal donor site. In contrast, hygromycin B inhibits the non‐enzymic translocation and the release of AcPhe‐tRNA from the ribosomal acceptor site promoted by depletion of NH + 4 ions. It is suggested that hygromycin B inhibits the movement of peptideyl‐tRNA associated with translocation by interfering with its exit from the ribosomal acceptor site. Hygromycin B has been previously described as an inducer of misreading [Davies, J., Gorini, L. and Davis, B. D. (1965) Mol. Pharmacol. 1 , 93–106]. It is now shown that the antibiotic interfaces with translation and induces misreading in the same poly(uridylic acid)‐directed system and in approximately the same range of concentrations. The results suggest a relationship between the ribosomal processes of aminoacyl‐tRNA recognition and translocation.