What is covalently attached to the $\alpha$ and $\gamma$ subunits of heterotrimeric G proteins in order to anchor the protein to the cell membrane?

Question

What is covalently attached to the

\alpha

and

\gamma

subunits of heterotrimeric G proteins in order to anchor the protein to the cell membrane?

What is covalently attached to the α\alphaα and γ\gammaγ subunits of heterotrimeric G proteins in order to anchor the protein to the cell membrane?