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. 2013 Mar 15;288(17):11854–11864. doi: 10.1074/jbc.M112.441915

FIGURE 1.

FIGURE 1.

Role of DrrA and FtsH in stable maintenance of DrrB. A, DrrA is required for stable expression of DrrB. Wild-type E. coli (TG1) cells expressing DrrAB (pDX101) or DrrB alone (pDX103) were grown at 37 °C to mid-log phase (A600 nm = 0.6) and induced with 0.25 mm IPTG for 3 h. 30 μg of membrane proteins were loaded onto 12% SDS-PAGE gels, followed by Western blotting against anti-DrrA (upper panel) and anti-DrrB (lower panel) antibodies. B, FtsH is responsible for proteolysis of unassembled DrrB. Wild-type E. coli (796) or the E. coli 797 (ftsHts) cells expressing DrrAB (pDX101) or DrrB alone (pDX103) were grown at 30 °C to mid-log phase and induced with 0.25 mm IPTG at either 30 or 42 °C for 3 h. Western blot analysis of the membrane fraction was carried out as in A. C, ClpA or the Lon protease is not involved in quality control of DrrB. Wild-type E. coli (796), E. coli 797 (ftsHts), E. coli SG1110 (Lon−), and E. coli SG1126 (ClpA−) cells expressing DrrAB (pDX101) or DrrB alone (pDX103) were grown at 30 or 37 °C to mid-log phase and induced with 0.25 mm IPTG at either 42 or 37 °C for 3 h, as indicated. Analysis was carried out as described in B above.