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Structural basis of FFAT motif-mediated ER targeting
Stephen E Kaiser1, Jason H Brickner, Amy R Reilein
1Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA.
Structure (London, England : 1993)
|July 12, 2005
Summary
The FFAT motif targets proteins to the endoplasmic reticulum (ER) by binding VAP proteins. Structural insights reveal this interaction is crucial for ER morphology.
Area of Science:
- Cell Biology
- Structural Biology
- Molecular Biology
Background:
- The FFAT motif acts as a protein targeting signal to the endoplasmic reticulum (ER) and nuclear membrane.
- VAP proteins, tethered to the ER cytoplasmic face, bind FFAT motifs.
Purpose of the Study:
- To determine the structural basis of FFAT motif-VAP protein interactions.
- To investigate the functional role of FFAT-mediated targeting in ER morphology.
Main Methods:
- X-ray crystallography was used to solve the structures of VAP-A MSP domain alone and in complex with an FFAT motif.
- A VAP mutant was designed to disrupt FFAT binding, and its function was tested in vitro and in yeast.
- The effect of the VAP mutant on ER morphology was examined in COS7 cells.
Main Results:
- The crystal structure revealed the molecular details of FFAT motif binding to VAP-A.
- The designed VAP mutant successfully disrupted FFAT interactions in vitro and blocked the function of its yeast homolog, Scs2p.
- Overexpression of the FFAT binding-defective VAP mutant significantly altered ER morphology in COS7 cells.
Conclusions:
- The study provides the structural foundation for FFAT-mediated ER targeting.
- FFAT-targeted proteins are important regulators of endoplasmic reticulum morphology.