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The preprotein conducting channel at the inner envelope membrane of plastids
Author(s) -
Heins Lisa,
Mehrle Alexander,
Hemmler Roland,
Wagner Richard,
Küchler Michael,
Hörmann Friederike,
Sveshnikov Dmitry,
Soll Jürgen
Publication year - 2002
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/21.11.2616
Subject(s) - inner membrane , biophysics , circular dichroism , vesicle , lipid bilayer , chemistry , membrane , ion channel , translocon , membrane protein , biology , biochemistry , receptor
The preprotein translocation at the inner envelope membrane of chloroplasts so far involves five proteins: Tic110, Tic55, Tic40, Tic22 and Tic20. The molecular function of these proteins has not yet been established. Here, we demonstrate that Tic110 constitutes a central part of the preprotein translocation pore. Dependent on the presence of intact Tic110, radiolabelled preprotein specifically interacts with isolated inner envelope vesicles as well as with purified, recombinant Tic110 reconstituted into liposomes. Circular dichroism analysis reveals that Tic110 consists mainly of β‐sheets, a structure typically found in pore proteins. In planar lipid bilayers, recombinant Tic110 forms a cation‐selective high‐conductance channel with a calculated inner pore opening of 1.7 nm. Purified transit peptide causes strong flickering and a voltage‐dependent block of the channel. Moreover, at the inner envelope membrane, a peptide‐sensitive channel is described that shows properties basically identical to the channel formed by recombinant Tic110. We conclude that Tic110 has a distinct preprotein binding site and functions as a preprotein translocation pore at the inner envelope membrane.