Co-sedimentation of Ffh with 70S ribosome from cells depleted of FtsY.

E. coli FJP10 harboring pT7-5/LacY were grown for 6.5 h with or without 0.05% arabinose (+/−ara). (A) Cells were fractionated and samples of extracts (E, 10 µg), supernatants (S, 10 µg) and pellets after ultracentrifugation (P, 4.5 µg) were analyzed by Western blotting. The Ffh band was quantified by densitometry. (B, C) The ultracentrifugation pellets (containing cytosolic ribosomes and membranes) were separated by sucrose gradient (see Material and Methods). (B) Optical density at 260 nm of each fraction. (C) Western blotting of each fraction with antibodies against the ribosomal protein L9, LacY, and Ffh.