FIG 4.

The C-terminal motif of a CtpA substrate is not sufficient for CtpA-dependent degradation. (A) PA3787 immunoblot analysis of equivalent amounts of whole-cell lysates of ctpA⁺ and ΔctpA strains. Strains contained an arabinose-inducible expression plasmid encoding wild-type PA3787 or a derivative with the 11 C-terminal amino acids from MepM added to its C terminus. (B) Anti-FLAG immunoblot analysis of equivalent amounts of whole-cell lysates of ctpA⁺ and ΔctpA strains. Strains contained an arabinose-inducible expression plasmid encoding P. aeruginosa MepM (Pa), E. coli MepM (Ec), or E. coli MepM with the 11 C-terminal amino acids from P. aeruginosa MepM added to its C terminus (+ Pa CT). The C termini of all proteins terminated with the FLAG tag sequence. For both panels, strains were grown in medium containing arabinose. Proteins were detected with ant-FLAG monoclonal antibodies, and a Ponceau S total protein stain of the same region of the nitrocellulose membrane is shown to document loading levels. Immunoblots are single representatives of several replicate experiments.