Distinct Pores for Peroxisomal Import of PTS1 and PTS2 Proteins
Malayko Montilla-Martinez, Sabrina Beck, Jessica Klumper, Michael Meinecke, Wolfgang Schliebs, Richard Wagner, Ralf Erdmann
email@example.com (R.W.), firstname.lastname@example.org (R.E.)
Two peroxisomal targeting signals, PTS1 and PTS2, direct folded proteins to the peroxisomal matrix. Montilla-Martinez et al. (2015) identify a PTS2-specific pore, which contains the PTS2 co-receptor Pex18 and the Pex14/Pex17-docking complex as major constituents. The data demonstrate that import of PTS1 and PTS2 proteins is performed by distinct pores.
Import of folded proteins into peroxisomes requires distinct
PTS2 pore is formed by the cytosolic co-receptor Pex18 and
docking complex Pex14/Pex17
The PTS2 receptor is not part of the unloaded pore
Complex gating of the PTS2 channel is voltage and cargo
Two peroxisomal targeting signals, PTS1 and PTS2, recognized by cytosolic receptors Pex5 and cooperating Pex7/Pex18, direct folded proteins to the peroxisomal matrix. A pore consisting of the PTS1 receptor Pex5 and the docking protein Pex14 imports PTS1 proteins. We identified a distinct PTS2-specific pore, which contains the PTS2 co-receptor Pex18 and the Pex14/Pex17-docking complex asmajor constituents. The estimated maximal pore size of 4.7 nm is large enough to allow import of folded PTS2 proteins. PTS2 cargo proteins modulate complex gating, open probability, and subconductance states of the pore. While the PTS1 channel is transiently activated by arriving receptor-cargo complexes, the reconstituted PTS2 channel is constitutively present in an open state. However, the cargo-loaded PTS2 channel is largely impermeable to solutes and ions. Our results demonstrate that import of PTS1 and PTS2 proteins does not converge at the peroxisomal membrane as previously anticipated but is performed by distinct pores.
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