Modifications post-traductionnelles des protéines par les lipides
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Covalent modifications of proteins by lipids were first associated with a passive role in membrane anchoring. Most recently, post-translational modifications of proteins by covalent lipids have been identified and they seem to have more than just a structural function. These are two types of post-translational modifications by lipids: palmitoylation and isoprenylation. The first is reversible and the modified proteins are found at the cytoplasmic face of the plasma membrane or at the endoplasmic reticulum. The second is irreversible and the modified proteins are found in almost all intracellular locations such as the cytoplasm, cell membrane and nucleus. Palmitoylation principally occurs on cysteines, but no consensus sequences have been identified, so far. Conversely, isoprenylation is found only on proteins with particular C-terminal sequences containing one or two cysteines. These two modifications were shown to be involved in the regulation of many proteins such as beta(2)- adrenergic receptor and Ras proteins. Post-translational modifications of proteins by covalent lipids appear to play an important role in the regulation of cellular functions.