Present address: Institute of Cell Biology, University of Bayreuth, NW1/B1, D-95440 Bayreuth, Germany.
KMS1 and KMS2, two plant endoplasmic reticulum proteins involved in the early secretory pathway
Article first published online: 23 MAR 2011
© 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd
The Plant Journal
Volume 66, Issue 4, pages 613–628, May 2011
How to Cite
Wang, P., Hummel, E., Osterrieder, A., Meyer, A. J., Frigerio, L., Sparkes, I. and Hawes, C. (2011), KMS1 and KMS2, two plant endoplasmic reticulum proteins involved in the early secretory pathway. The Plant Journal, 66: 613–628. doi: 10.1111/j.1365-313X.2011.04522.x
- Issue published online: 10 MAY 2011
- Article first published online: 23 MAR 2011
- Accepted manuscript online: 5 FEB 2011 04:00AM EST
- Received 26 October 2010; revised 13 January 2011; accepted 2 February 2011; published online 23 March 2011.
- endoplasmic reticulum;
- Golgi apparatus;
- redox-sensitive GFP;
- protein secretion;
We have identified two endoplasmic reticulum (ER)-associated Arabidopsis proteins, KMS1 and KMS2, which are conserved among most species. Fluorescent protein fusions of KMS1 localised to the ER in plant cells, and over-expression induced the formation of a membrane structure, identified as ER whorls by electron microscopy. Hydrophobicity analysis suggested that KMS1 and KMS2 are integral membrane proteins bearing six transmembrane domains. Membrane protein topology was assessed by a redox-based topology assay (ReTA) with redox-sensitive GFP and confirmed by a protease protection assay. A major loop domain between transmembrane domains 2 and 3, plus the N- and C-termini were found on the cytosolic side of the ER. A C-terminal di(tri)-lysine motif is involved in retrieval of KMS1 and deletion led to a reduction of the GFP–KMS1 signal in the ER. Over-expression of KMS1/KMS2 truncations perturbed ER and Golgi morphology and similar effects were also seen when KMS1/KMS2 were knocked-down by RNA interference. Microscopy and biochemical experiments suggested that expression of KMS1/KMS2 truncations inhibited ER to Golgi protein transport.