Tryptophan-dependent sensitized photoinactivation of colicin E1 channels in bilayer lipid membranes

• Published in: FEBS letters Vol. 505; no. 1; pp. 147 - 150
• Main Authors: Rokitskaya, T.I., Zakharov, S.D., Antonenko, Yu.N., Kotova, E.A., Cramer, W.A.
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 07.09.2001
• Subjects: Amino Acid Substitution; BLM, bilayer lipid membrane; Colicins - chemistry; Colicins - genetics; Indoles; Ion channel; Lipid bilayer; Lipid Bilayers - chemistry; Mutation; Organometallic Compounds; Osmolar Concentration; P178, 178-residue C-terminal colicin E1 channel polypeptide; Photochemistry; Photosensitized inactivation; Reactive oxygen species; Toxin; Tryptophan; Tryptophan - chemistry; Toxin; Reactive oxygen species; P178, 178-residue C-terminal colicin E1 channel polypeptide; Photosensitized inactivation; Lipid bilayer; Tryptophan; BLM, bilayer lipid membrane; Ion channel
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/S0014-5793(01)02811-3

The bacterial toxin colicin E1 is known to induce voltage-gated currents across a planar bilayer lipid membrane. In the present study, it is shown that the colicin-induced current decreased substantially upon illumination of the membrane in the presence of the photosensitizer, aluminum phthalocyanine. This effect was almost completely abolished by the singlet oxygen quencher, sodium azide. Using single tryptophan mutants of colicin E1, Trp495 was identified as the amino acid residue responsible for the sensitized photodamage of the colicin channel activity. Thus, the distinct participation of a specific amino acid residue in the sensitized photoinactivation of a defined protein function was demonstrated. It is suggested that Trp495 is critical for the translocation and/or anchoring of the colicin channel domain in the membrane.