this approach indicated a half-life for N-Ras palmitoylation of 20 min (Magee et al., 1987) and showed that palmitoylation of G subunits of heterotrimeric G proteins can be modulated by agonist stimulation (Degtyarev et al., 1993; Mumby et al., 1994; Wedegaertner and Bourne, 1994) .