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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geprüft am 15.05.2024