Identification of a novel function for the FtsL cell division protein from Escherichia coli K12

► FtsL is shown to have a novel function, the generation of Zn(II)-sensitivity. ► Specific residues within the primary sequence identified as associated with Zn(II)-ion sensitivity. ► Mutated FtsL derivatives capable of supporting cell-division. ► Loss of a cysteine-pair in FtsL results in sensitivity to elevated Zn(II). Analysis of the essential cell division protein FtsL demonstrates the partial conservation of a cysteine-pair within the trans-membrane region which itself is flanked by histidine-pairs in the cytosol and periplasm. Similar arrangements of such amino acids are seen in proteins known to transport/bind metal ions in biological systems. Heterologous expression of ftsL in Escherichia coli K12 confers a Zn(II)-sensitive phenotype and alteration of the candidate metal-ion binding residues cysteine or histidine substantially alters this phenotype. Whilst the cysteine/histidine replacement derivatives of ftsL were able to complement an otherwise ftsL-null strain, the derivative carrying ftsL lacking the cysteine pair was sensitive to raised metal-ion concentrations in the media. We show that ftsL can confer a metal-ion sensitive phenotype and that trans-membrane cysteine residues play a role in FtsL function in elevated metal-ion concentrations.