The pseudouridine synthase RluD is required for normal ribosome assembly and function in Escherichia coli

Polyphenyalanine synthesis by wild-type and mutant 70S ribosomes. Polyphenylalanine synthesis was performed as described in Materials and Methods. (A) 70S ribosome fractions were isolated from sucrose gradients at 15 mM Mg⁺⁺ concentration during lysis and sedimentation. Nine individual experiments were performed using 70S fractions from four wild-type and seven mutant ribosome preparations; MG1655/I⁻::tet 0.5 A₂₆₀ (closed squares) or ΔrluD::kan/I⁻::tet 0.5 A₂₆₀ units (closed circles). Four individual experiments were performed using 70S fractions from two wild-type and four mutant ribo-some preparations; MG1655/I⁻::tet 1.0 A₂₆₀ unit (open squares) or ΔrluD::kan/I⁻::tet 1.0 A₂₆₀ unit (open circles). (B) Three individual experiments were performed using 70S fractions from two wild-type and three mutant ribosome preparations (lysis 6 mM and sedimentation 15 mM Mg⁺⁺). Symbols are the same as for A.