Lanthanide Ions Unfolded Im9

Colicins are plasmid encoded antibacterial proteins synthesised by bacteria to kill other bacteria. they have an n-terminal translocation domain, a central receptor recognition domain and a cterminal cytotoxic domain. this study focused on lanthanide ion binding to the e9 cognate immunity protein (im9), which neutralises the killing action of colicin e9 in its producing cell. the effects of most of the lanthanide ions on binding to these proteins were investigated. changes in protein fluorescence emission and luminescence resonance energy transfer to eu^3+ and tb^3+, which are the most strongly emitting lanthanide ions, were monitored by using luminescence spectroscopy. denaturation of im9 was revealed when lanthanide ion was added as indicated by their tryptophan fluorescence and luminescence resonance energy transfer from tryptophan to eu^3+ and tb^3+.