Structural analyses of a channel-forming fragment of colicin E1 incorporated into lipid vesicles. Fourier-transform infrared and tryptophan fluorescence studies

• Published in: The Journal of biological chemistry Vol. 266; no. 21; pp. 13537 - 13543
• Main Authors: SUGA, H, SHIRABE, K, YAMAMOTO, T, TASUMI, M, UMEDA, M, NISHIMURA, C, NAKAZAWA, A, NAKANISHI, M, ARATA, Y
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 25-07-1991
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Biological and medical sciences; Circular Dichroism; colicin E1; Colicins - chemistry; Energy Transfer; Fourier Analysis; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Ion Channels - physiology; Membrane Lipids; Membrane Proteins - chemistry; Miscellaneous; Molecular Sequence Data; Peptide Fragments; Protein Conformation; Proteins; Pyrenes - chemistry; Spectrometry, Fluorescence; Spectrophotometry, Infrared; Thermolysin; Tryptophan - chemistry; Proteins; Infrared spectrometry; Fourier transformation; C terminal peptide; Peptide fragment; Circular dichroism spectrometry; Liposome; Membrane channel; Secondary structure; Energy transfer; Aminoacid sequence
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)92731-6

Structural changes upon binding to the membrane of a COOH-terminal channel-forming thermolytic fragment of colicin E1 have
been studied by means of a variety of spectroscopic techniques. Circular dichroism measurements show that the thermolytic
fragment predominantly takes a helical structure in aqueous and detergent solutions. Fourier transform infrared spectroscopic
measurements indicate that the content of the beta-structure is significantly increased when the thermolytic fragment is bound
to vesicles. On the basis of the result of tryptophan fluorescence measurements, we have concluded that each of the three
tryptophan residues of the thermolytic fragment exists in different environments, i.e. one is buried in the lipid bilayer,
one exists on the cis side of the vesicles, and one exists near the surface of the lipid bilayer. The Fourier transform infrared
and fluorescence data have been used along with the crystal structure of colicin A, which is highly homologous to colicin
E1 in structure and function, to propose a model of the thermolytic fragment bound to the lipid vesicles.