These authors contributed equally to the work.
Topology of the microsomal glycerol-3-phosphate acyltransferase Gpt2p/Gat1p of Saccharomyces cerevisiae
Article first published online: 12 OCT 2012
© 2012 Blackwell Publishing Ltd
Volume 86, Issue 5, pages 1156–1166, December 2012
How to Cite
Pagac, M., Vazquez, H. M., Bochud, A., Roubaty, C., Knöpfli, C., Vionnet, C. and Conzelmann, A. (2012), Topology of the microsomal glycerol-3-phosphate acyltransferase Gpt2p/Gat1p of Saccharomyces cerevisiae. Molecular Microbiology, 86: 1156–1166. doi: 10.1111/mmi.12047
- Issue published online: 26 NOV 2012
- Article first published online: 12 OCT 2012
- Accepted manuscript online: 27 SEP 2012 10:10PM EST
- Manuscript Accepted: 18 SEP 2012
- Swiss National Science Foundation. Grant Numbers: 31-67188.01, CRSI33_125232/1
All glycerophospholipids are made from phosphatidic acid, which, according to the traditional view, is generated at the cytosolic surface of the ER. In yeast, phosphatidic acid is synthesized de novo by two acyl-CoA-dependent acylation reactions. The first is catalysed by one of the two homologous glycerol-3-phosphate acyltransferases Gpt2p/Gat1p and Sct1p/Gat2p, the second by one of the two 1-acyl-sn-glycerol-3-phosphate acyltransferases Slc1p and Ale1p/Slc4p. To study the biogenesis and topology of Gpt2p we observed the location of dual topology reporters inserted after various transmembrane helices. Moreover, using microsomes, we probed the accessibility of natural and substituted cysteine residues to a membrane impermeant alkylating agent and tested the protease sensitivity of various epitope tags inserted into Gpt2p. Finally, we assayed the sensitivity of the acyltransferase activity to membrane impermeant agents targeting lysine residues. By all these criteria we find that the most conserved motifs of Gpt2p and its functionally relevant lysines are oriented towards the ER lumen. Thus, the first step in biosynthesis of phosphatidic acid in yeast seems to occur in the ER lumen and substrates may have to cross the ER membrane.