2DE analysis of Salmonella Typhimurium luxS mutants. (A) Total gel image of wildtype S. Typhimurium proteins. The two LuxS forms are indicated with an arrow. Based on pI calculations, the right spot corresponds to native LuxS and the left spot carries a posttranslational modification. (B-J) Close-up view of the area of the LuxS spots in a luxS mutant carrying different LuxS complementation constructs. (B) negative control - empty vector; (C) wildtype LuxS; (D) LuxS-Y88F; (E) LuxS-Y126F; (F) LuxS-Y131F; (G) LuxS-Y88D; (H) LuxS-Y126D; (I) LuxS-Y131D; (J) LuxS-C83A. Remark that in theory, on the gels from which panels G-I are taken, an additional modified LuxS spot is expected, accumulating the Y to D mutation and the cysteine modification.