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J Mol Biol. 1992 Apr 20;224(4):1011-27.

Kinetic properties of Escherichia coli ribosomes with altered forms of S12.

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University of Uppsala, Department of Molecular Biology, Sweden.


E. coli ribosomes with alterations in S12 leading to streptomycin resistance (SmR), dependence (SmD) and pseudodependence (SmP) were studied with the quench-flow technique. Kinetic changes at the various steps of the elongation cycle were identified. The rate of hydrolysis of GTP in the ternary complex in the ribosomal A-site is decreased drastically in SmD and moderately in SmP in relation to wild-type ribosomes. Addition of streptomycin restores much of the wild-type behaviour. The SmD, SmP and SmR ribosomes have an enhanced GTP-hydrolysis idling reaction on EF-Tu, which is correlated with how aggressive proofreaders these ribosomes are in steady-state assays. We use our in vitro findings to discuss the in vivo physiology of these mutants as well as mechanistic features of E. coli translation.

[Indexed for MEDLINE]

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