FIG 4.

Effect of ftsL activation and dominant negative mutations on the rescue of FtsL^Δ1-30. (A) ftsL^Δ1-30 is rescued by ftsL activation mutations, which is negated by an ftsL dominant negative mutation. SD439 (ftsL::kan/pSD296 [P_ara::ftsL]) was transformed with derivatives of pKTP105 (P_T5::ftsL) carrying various alleles of ftsL inducible with IPTG. The strains were spotted on plates without arabinose (to deplete WT ftsL) but with IPTG (to induce the various alleles of ftsL present in derivatives of pKTP105). The cartoons on the right depict the interpretation of the results. (B) Overexpression of ftsW^M269I rescues ftsL^Δ1-30. SD399 (ftsL::kan/pSD256 [repA^TS P_syn135::ftsL]) carrying pKTP107 (P_ara::ftsL^Δ1-30) was transformed with compatible plasmids expressing different alleles of ftsW (derivatives of pSEB429 [P₂₀₄::ftsW]) under the control of an IPTG-inducible promoter. Transformants were spotted on plates at 37°C (to deplete WT ftsL) in the presence of 0.2% arabinose (to induce ftsL alleles contained on the plasmids) and increasing concentrations of IPTG (to induce ftsW alleles). The cartoon indicates that FtsW^M269I is recruited by FtsL^Δ1-30. (C) Dominant negative ftsL mutations negate rescue of ftsL^Δ1-30 by ftsW^M269I. Strain SD399 (ftsL::kan/pSD256 [repA^TS P_syn135::ftsL]) was transformed with a plasmid (derivatives of pKTP107 [P_ara::ftsL^Δ1-30]) with ftsL^Δ1-30 under arabinose promoter control and a compatible plasmid (pSEB429 [P₂₀₄::ftsW]) that carries ftsW or ftsW^M269I under the control of an IPTG-inducible promoter. The presence of a dominant negative ftsL mutation negates rescue by the activated FtsW.