4.4 Lipidation
Lipid modification occurs in both prokaryotes and eukaryotes, including viruses. Lipidated proteins have an increased affinity for membranes, and the preferential partition of lipid-anchored proteins provides a number of physiological benefits, such as spatial specificity, increased local concentration and faster protein–protein interactions. A number of C-terminal motifs are sites for lipidation, including-CaaX, -CC and –CXC, where X is any amino acid and a is an aliphatic residue.
Prenylation and acylation affect the ability of the protein to interact with membranes (Table 6), which in turn alters their ability to interact with substrates and can also affect sorting to different compartments. For example, segregation to the apical and basolateral membranes appears to involve partitioning of newly synthesised proteins into glycosphingolipid-enriched domains.
Table 6 Lipid modification of proteins and their membrane affinity.
| Modification | Addition | Substrates | Membrane affinity, KD |
|---|---|---|---|
| farnesylation | post-translation | cytosolic proteins | 100 μmol l−1 |
| geranylgeranylation | post-translation | cytosolic proteins | 2 μmol l−1 |
| N-myristoylation | co-translation | nascentpolypeptide | 80 μmol l−1 |
| palmitoylation | post-translation | membrane protein | 5 μmol l−1 |