Document Detail

PSI1 is responsible for the stearic acid enrichment that is characteristic of phosphatidylinositol in yeast.
MedLine Citation:
PMID:  19796168     Owner:  NLM     Status:  MEDLINE    
In yeast, both phosphatidylinositol and phosphatidylserine are synthesized from cytidine diphosphate-diacylglycerol. Because, as in other eukaryotes, phosphatidylinositol contains more saturated fatty acids than phosphatidylserine (and other phospholipids), it has been hypothesized that either phosphatidylinositol is synthesized from distinct cytidine diphosphate-diacylglycerol molecules, or that, after its synthesis, it is modified by a hypothetical acyltransferase that incorporates saturated fatty acid into neo-synthesized molecules of phosphatidylinositol. We used database search methods to identify an acyltransferase that could catalyze such an activity. Among the various proteins that we studied, we found that Psi1p (phosphatidylinositol stearoyl incorporating 1 protein) is required for the incorporation of stearate into phosphatidylinositol because GC and MS analyses of psi1Delta lipids revealed an almost complete disappearance of stearic (but not of palmitic acid) at the sn-1 position of this phospholipid. Moreover, it was found that, whereas glycerol 3-phosphate, lysophosphatidic acid and 1-acyl lysophosphatidylinositol acyltransferase activities were similar in microsomal membranes isolated from wild-type and psi1Delta cells, microsomal membranes isolated from psi1Delta cells are devoid of the sn-2-acyl-1-lysolysophosphatidylinositol acyltransferase activity that is present in microsomal membranes isolated from wild-type cells. Moreover, after the expression of PSI1 in transgenic psi1Delta cells, the sn-2-acyl-1-lysolysophosphatidylinositol acyltransferase activity was recovered, and was accompanied by a strong increase in the stearic acid content of lysophosphatidylinositol. As previously suggested for phosphatidylinositol from animal cells (which contains almost exclusively stearic acid as the saturated fatty acid), the results obtained in the present study demonstrate that the existence of phosphatidylinositol species containing stearic acid in yeast results from a remodeling of neo-synthesized molecules of phosphatidylinositol.
Marina Le Guédard; Jean-Jacques Bessoule; Valérie Boyer; Sophie Ayciriex; Gisèle Velours; Willem Kulik; Christer S Ejsing; Andrej Shevchenko; Denis Coulon; René Lessire; Eric Testet
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2009-10-01
Journal Detail:
Title:  The FEBS journal     Volume:  276     ISSN:  1742-4658     ISO Abbreviation:  FEBS J.     Publication Date:  2009 Nov 
Date Detail:
Created Date:  2009-10-14     Completed Date:  2009-10-28     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101229646     Medline TA:  FEBS J     Country:  England    
Other Details:
Languages:  eng     Pagination:  6412-24     Citation Subset:  IM    
CNRS Laboratoire de Biogenèse Membranaire, CNRS UMR5200, Université de Bordeaux, France.
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MeSH Terms
Acyltransferases / metabolism
Microsomes / chemistry
Phosphatidylinositols / analysis*,  metabolism*
Saccharomyces cerevisiae / metabolism*
Saccharomyces cerevisiae Proteins / physiology*
Stearic Acids / analysis*
Reg. No./Substance:
0/Phosphatidylinositols; 0/Saccharomyces cerevisiae Proteins; 0/Stearic Acids; 57-11-4/stearic acid; EC 2.3.-/Acyltransferases; EC 2.3.1.-/lysophosphatidylinositol acyltransferase

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