Table 11.1.
Sites of G protein lipid modifications
| Gα subunits | N-termini of α subunits | Lipid modification |
|---|---|---|
| αi1 | MGCTLSAEDKAAVERSKMID- | Myristoylation, Palmitoylation |
| αo1 | MGCTLSAEERAALERSKAIE- | Myristoylation, Palmitoylation |
| αZ | MGCRQSSEEKEAARRSRRID- | Myristoylation, Palmitoylation |
| αt | MGAGASAEEKHSREL- | Myristoylation |
| αs | MGCLGNSKTEDQRNEEDAQR- | Palmitoylation |
| αq | MTLESIMACCLSEEAKEARR- | Palmitoylation |
| α14 | MAGCCCLSAEEKESQRISAE- | Palmitoylation |
| α16 | MARSLRWRCCPWCLTEDEKA- | Palmitoylation |
| α12 | MSGVVRTLSRCLLPAEAGAR- | Palmitoylation |
| α13 | MADFLPSRSVLSVCFPGCVL- | Palmitoylation |
|
| ||
| Gγ subunits | C-termini of γ subunits | Lipid modification |
|
| ||
| γ1 | -KGIPEDKNPFKELKGGC ↓VIS | Farnesylation |
| γ2 | -TPVPASENPFREKKFFC ↓AIL | Geranylgeranylation |
The N-terminal sequences of several Gα and the C-terminal sequences of two Gγ are shown. Myristate links through an amide bond to an N-terminal glycine after removal of the initiating methionine as indicated by G. Palmitate attaches via a thioester bond to cysteine (in bold italics) residues near the N-terminus of Gα. γ1 and γ2 are isoprenylated through a thioether bond to a cysteine, indicated by C. After isoprenylation the C-terminal three amino acids are removed (↓), and the new C-terminus is carboxyl methylated. This is a representative listing of G protein subunits. In humans, 16 genes encode Gα (plus additional splice variants), 5 genes encode Gβ (Gβ proteins are not known to be lipid-modified), and 12 genes encode Gγ. Reprinted with permission from Marrari et al. (2007). Copyright 2007 American Chemical Society