The open pore of SecYEG does not show physiologically relevant ion selectivity

Description

The open pore of SecYEG does not show physiologically relevant ion selectivity. Denis Knyazev, Lukas Winter, Nicole Ollinger, Christine Siligan, and Peter Pohl Institut für Biophysik, Johannes Kepler Universität Linz, Gruberstrasse 40, A-4020 Linz, Austria The bacterial translocon SecYEG resides in the cytoplasmic membrane and either translocates secretory proteins from the cytoplasm to the periplasm or reconstitutes transmembrane proteins into the cytoplasmic membrane. In its open and unoccupied state, it is a big ionic channel of ~0.5 nS conductivity under physiological conditions [1]. Unhindered proton flow through it would be lethal due to collapse of transmembrane proton gradient. To test the ion selectivity of SecYEG we reconstituted it into lipid bilayers and measured the reversal potential under asymmetric salt. Both the channel activated by signal peptides and the plug deletion mutant showed a very modest preference of anions over cations (the permeability ratio is 4.1±1.6). We conclude that SecY is a poor barrier even for K+ ions, and the opened channel on its own cannot sustain the proton motif force across the cytoplasmic membrane. 1. Sapar M. Saparov, Karl Erlandson, Kurt Cannon, Julia Schaletzky, Sol Schulman, Tom A. Rapoport, and Peter Pohl (2007). Determining the Conductance of the SecY Protein Translocation Channel for Small Molecules. Mol. Cell 26: 501-509. 2. Denis G. Knyazev, Alexander Lents, Eberhard Krause, Nicole Ollinger, Christine Siligan, Daniel Papinski, Lukas Winter, Andreas Horner, and Peter Pohl. The Bacterial Translocon SecYEG Opens upon Ribosome Binding. J. Biol. Chem. 288 (25): 17941-17946.

Period	17 Jul 2013
Event title	European Biophysics Conference 2013, Lissabon Portugal
Event type	Conference
Location	PortugalShow on map