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. 2001 Aug 21;98(18):10096–10101. doi: 10.1073/pnas.171319598

Figure 3.

Figure 3

Influence of changing monovalent ion concentration and temperature on the 50S subunit's pH-dependent DMS reactivity at A2451 and ability to perform peptidyl transfer. Unm, unmodified ribosomes. (A) Heat activation of 50S subunits in K+ (lanes 6–8) or NHInline graphic (lanes 12–14) results in loss of pH-dependent DMS reactivity at A2451. (B) Heat incubation in the absence of monovalent cation (lanes 6–8) or in the presence of Na+ (lanes 12–14) does not result in loss of pH-dependent DMS reactivity at A2451. (C) Increasing concentrations of K+ (lanes 3–5) or NHInline graphic (lanes 6–8) at constant pH (6.5) at 0°C results in increasing DMS reactivity of A2451. (D) 50S subunits shown to exhibit pH-dependent DMS reactivity at A2451 cannot perform peptidyl transferase as assayed by the fragment reaction. 50S preincubation conditions are as shown.