Influence of spermine on spontaneous and enzymatic translocation

Copyright information:Taken from "Localization of spermine binding sites in 23S rRNA by photoaffinity labeling: parsing the spermine contribution to ribosomal 50S subunit functions"Nucleic Acids Research 2005;33(9):2792-2805.Published online 16 May 2005PMCID:PMC1129027.© The Author 2005. Published by Oxford University Press. All rights reserved () Time course of (circles) enzymatic and (squares) spontaneous translocation. Aliquots of pre-translocation complex, i.e. poly(U)-programmed 70S ribosomes occupied at the P- and A-sites with tRNA and Ac[H]Phe-tRNA, respectively, were incubated for the indicated time intervals in buffer A containing 0.12 mM GTP, (open symbols) in the absence or (filled symbols) in the presence of 50 μM spermine. Enzymatic translocation was obtained by the addition of 15 nM EFG in the incubation mixture. Inset, dependence of spontaneous translocation on spermine concentration. To a fixed amount of pre-translocation complex, increasing concentrations of spermine were added and translocation was allowed to proceed for 10 min at 25°C. () Dependence of translocation on EFG concentration. Pre-translocation complex was incubated with different amounts of EFG for 1 min at 25°C (open circles) in the absence or (filled circles) in the presence of 50 μM spermine. In all drawings, translocation of 100% represents conversion of all ribosomes at the pre-translocation state into the post state.