Acidic pH-Induced Membrane Insertion of Colicin A into E. coli Natural Lipids Probed by Site-Directed Spin Labeling

Autor(en): Pulagam, Lakshmi Padmavathi
Steinhoff, Heinz-Juergen 
Stichwörter: Biochemistry & Molecular Biology; BOUND STATE; channel activity in liposomes; closed channel state; E1 CHANNEL DOMAIN; HELIX-G; HIGH-FIELD EPR; insertion-competent state; NITROXIDE MOTION; PORE-FORMING DOMAIN; PROTEIN; SIDE-CHAINS; site-directed spin labeling; STRUCTURAL DETERMINANTS; TRANSFER DISTANCE MEASUREMENTS; water-soluble pore-forming toxin
Erscheinungsdatum: 2013
Herausgeber: ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
Journal: JOURNAL OF MOLECULAR BIOLOGY
Volumen: 425
Ausgabe: 10
Startseite: 1782
Seitenende: 1794
Zusammenfassung: 
Colicin A is a pore-forming toxin that forms a voltage-gated channel in the inner membrane of the target bacteria. The structures of the closed and open channel states of membrane-bound colicin A are not resolved. In the present site-directed spin-labeling study, the insertion-competent state of colicin A is provoked by an acidic pH jump prior to the insertion into liposomes prepared from Escherichia coli natural lipids. The membrane-bound colicin A is able to open a voltage-dependent channel as demonstrated by the efflux of tempophosphate spin label from the lumen of liposomes. The EPR spectra of spin-labeled colicin A variants in the membrane-bound closed channel state reveal a conformational equilibrium with resolved interhelical tertiary contacts. The spin label accessibility and polarity profiles suggest the amphipathic helices (H1-H7 and H10) to be located in the membrane close to the membrane-water interface and the hydrophobic hairpin (H8 and H9) to be immersed more deeply in the membrane. (C) 2013 Elsevier Ltd. All rights reserved.
ISSN: 00222836
DOI: 10.1016/j.jmb.2013.01.037

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