FIG. 2.

Specific interaction between YajL and ribosomal proteins. Ribosomal proteins from the wild-type strain were prepared by incubating ribosomes (prepared as described in reference 9) overnight in 10 mM Tris (pH 7.6), 6 mM MgCl₂, 60 mM NH₄Cl, 1 mM 2-mercaptoethanol, 6 M urea, and 1 M LiCl at 0°C as described by Nomura and colleagues (18). The samples were centrifuged at 35,000 × g for 10 min in order to remove the precipitated RNA, and the ribosomal proteins (800 μg) were diluted 8-fold in 250 μl of 40 mM sodium phosphate (pH 8) and 100 mM NaCl in the absence (lane 1) or in the presence (lane 2) of 80 μg of purified His-tagged YajL. Proteins retained on nickel affinity columns (His-Select nickel affinity gel, 200-μl-bed-volume; Sigma-Aldrich) were analyzed by 15% acrylamide SDS-PAGE (silver stained) and identified by matrix-assisted laser desorption ionization-time of flight/time of flight (MALDI-TOF/TOF) mass spectrometry (with an Applied Biosystems 4800 proteomics analyzer).