YidC alters conductivity and ion selectivity of the bacterial translocation channel SecYEG
Sprache des Vortragstitels:
Englisch
Original Tagungtitel:
58th Annual Biophysical Society Meeting: Bridging the Sciences to Explore Biology
Sprache des Tagungstitel:
Englisch
Original Kurzfassung:
YidC alters conductivity and ion selectivity of the bacterial translocation channel SecYEG
Lukas Winter1,*, Denis Knyazev1,*, Nicole Ollinger1, Andreas Vogt2,3,4, Christine Siligan1, Hans-Georg Koch2,3, and Peter Pohl1,#
1Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, A-4020 Linz, Austria; 2Institut für Biochemie und Molekularbiologie, ZBMZ, and 3Spemann-Graduate School of Biology and Medicine (SGBM) and 4Faculty of Biology, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany
During protein transport across the membrane the bacterial translocon SecYEG must maintain the barrier to cations and protons in order to preserve the proton motif force. In vivo and in vitro experiments with SecYEG mutants in the bacterial plasma membrane attributed the preservation of the proton motif force to an intrinsic anion-selectivity of the channel1. Since potential residues responsible for selective cation exclusion are not easily recognizable in the SecYEG structure we tested the ion selectivity of (i) the purified wild type SecYEG channel, which was opened by ribosome binding2 and (ii) the purified plugless SecYEG mutant after reconstitution into planar bilayers. In both cases, reversal potential measurements under conditions of a transmembrane salt gradient did not reveal physiologically relevant ion selectivity. Upon co-reconstitution of SecYEG with YidC we found decreased single channel conductivity and increased anion selectivity of SecYEG. Combined, both factors acted to decrease the cation leak through SecYEG by an order of magnitude. Additional experiments on YidC reconstituted into planar bilayers suggest that YidC itself forms a pore which is opened by ribosome binding.
1. Park, E. and Rapoport, T. A. (2011) Nature 473, 239-242
2. Knyazev, D. G., Lents, A., Krause, E., Ollinger, N., Siligan, C., Papinski, D., Winter, L., Horner, A., and Pohl, P. (2013) J. Biol. Chem. 288, 17941-17946
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