Identification of a chameleon-like pH-sensitive segment within the colicin E1 channel domain that may serve as the pH-activated trigger for membrane bilayer association

Biochemistry
A R MerrillA G Szabo

Abstract

In vitro, the channel-forming domain of colicin E1 requires activation by acidic pH (<4.5) or detergents. The activation of this domain to its insertion-competent state results in an increased ability of the protein to dock onto and to form channels in artificial membranes. Fluorescence methods were used to characterize the conformational changes occurring in a channel-forming peptide of colicin E1 in solution with pH. The 178-residue thermolytic fragment of colicin E1 contains three Trp residues, W-424, W-460, and W-495. In order to study the structural and dynamic requirements for activation of the C-terminal domain of colicin E1, single-Trp-containing peptides were prepared by site-directed mutagenesis. All of the mutant peptides displayed in vitro channel activity and cellular cytotoxicity similar to the those of wild-type peptide. Two Trp residues, W-413 and W-424, exhibited pH-sensitive fluorescence parameters. Upon acidification (pH 6.0 --> 3.5), the fluorescence quantum yield of W-413 and W-424 increased 50% and 80%, respectively, indicating a significant change in the local environment of the peptide segment containing these two Trp residues. The fluorescence decay of W-413 and W-424 was best fit by three fluorescence ...Continue Reading

Citations

Sep 8, 1998·Current Opinion in Structural Biology·R M StroudD Freymann
Oct 25, 2000·Photochemistry and Photobiology·J R Lakowicz
Oct 14, 2010·Proteins·Lidia Prieto, Themis Lazaridis
Aug 24, 1999·The Journal of Biological Chemistry·M C Tory, A R Merrill
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Oct 31, 2003·The Journal of Biological Chemistry·Kenichiro FujiwaraMasahiro Shirakawa
Jun 6, 2000·American Journal of Physiology. Cell Physiology·J I Kourie, A A Shorthouse

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