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Updated: Aug 11, 2026

Examining the Conformational Dynamics of Membrane Proteins in situ with Site-directed Fluorescence Labeling
Published on: May 29, 2011
Identification of a translocated protein segment in a voltage-dependent channel
S L Slatin1, X Q Qiu, K S Jakes
1Albert Einstein College of Medicine, Department of Physiology and Biophysics, Bronx, New York 10461.
Abstract:
Voltage-gated channels undergo a conformational change in response to changes in transmembrane voltage. Here we use site-directed biotinylation to create conformation-sensitive sites on colicin Ia, a bacteriocidal protein that forms a voltage-sensitive membrane channel, which can be monitored by electrophysiological methods. We investigated a model of gating developed for the partly homologous colicin E1 that is based on the insertion of regions of the protein into the membrane in response to cis-positive voltages. Site-directed cysteine mutagenesis, followed by chemical modification, was used to attach a biotin molecule covalently to a series of unique sites on colicin Ia. The modified protein was incorporated into planar lipid membranes, where the introduced biotin moiety served as a site to bind the water-soluble protein streptavidin, added to one side of the membrane or the other. Our results show that colicin gating is associated with the translocation across the membrane of a segment of the protein of at least 31 amino acids.
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