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Two tail-anchored protein variants, differing in transmembrane domain length and intracellular sorting, interact differently with lipids
- Source :
- Proceedings of the National Academy of Sciences of the United States. Nov 8, 2005, Vol. 102 Issue 45, p16269, 6 p.
- Publication Year :
- 2005
-
Abstract
- C-tail-anchored (TA) proteins often require a transmembrane domain of moderate hydrophobicity to maintain their endoplasmic reticulum residence, but the suggested role of protein--lipid interactions in this phenomenon has not been established. Here, we studied the interaction of TA proteins with lipids by differential scanning calorimetry by using a model system consisting of liposomes embedding either of two forms of cytochrome [b.sub.5]: the endoplasmic reticulum-resident wild-type ([b.sub.5]wt) and a mutant thereof ([b.sub.5]ext), that contains five extra nonpolar amino acids in its transmembrane domain and, therefore, reaches the plasma membrane. The proteins were incorporated into liposomes of palmitoyloleyl-phosphatidylcholine (POPC) or POPC mixed with either distearoyl-phosphatidylserine (DSPS), palmitoyl-oleyl-phosphatidylserine (POPS), distearoyl-phosphatidylcholine (DSPC), or C16-ceramide (CER). POPC liposomes displayed a single thermotropic transition centered at -3.4[degrees]C. When present, the second lipid formed a domain within the POPC bilayer, as indicated by the appearance of an additional peak. This peak was centered at temperatures close to 0[degrees]C in the case of liposomes containing 10% CER, DSPS, and POPS and at 23[degrees]C in the case of DSPC, likely reflecting a higher degree of molecular packing for DSPC domains. In DSPS/POPC, POPS/POPC, or CER/POPC, but not in DSPC/POPC liposomes, the insertion of [b.sub.5]wt increased, whereas [b.sub.5]ext decreased, the relative contribution to the total enthalpy of the higher temperature, phase-separated component. These results were confirmed with fluorescence measurements by using pyrene-labeled phospholipids. The dissimilar interaction with lipids of these two differently localized TA proteins could have implications for their intracellular sorting. cytochrome [b.sub.5] | differential scanning calorimetry | endoplasmic reticulum | lipid domains | liposomes
Details
- Language :
- English
- ISSN :
- 00278424
- Volume :
- 102
- Issue :
- 45
- Database :
- Gale General OneFile
- Journal :
- Proceedings of the National Academy of Sciences of the United States
- Publication Type :
- Academic Journal
- Accession number :
- edsgcl.139472208