Fig. 1. Post-translational modification and expression patterns of Rho proteins. (A) Representation of the different C-termini, the post-translational lipid modifications that occur at these sites in Rho proteins, and the additional membrane targeting signals. The first four represent variations seen in CAAX motif-terminating Rho GTPases. The CAAX sequence signals for either farnesyl (F) or geranylgeranyl (GG) isoprenoid modification of the cysteine residue, followed by proteolytic removal of the AAX residues, and carboxylmethylation (OMe) of the now-terminal cysteine residue. Rac1 (also Rac2, Rac3, RhoA, RhoC and Cdc42) has a polybasic [K/R] sequence followed by a GG-modified cysteine. Rnd proteins contain a polybasic sequence followed by an F modification of the cysteine. TC10 (and probably TCL) is modified by both F and a palmitoyl (P) group. RhoB is modified by a P group at one cysteine and either a F or GG group at the other cysteine. RhoD is also F-modified, whereas Rif is expected to be GG-modified. These modifications have been verified by direct or indirect analyses (Adamson et al., 1992b; Ando et al., 1992; Foster et al., 1996; Michaelson et al., 2001; Murphy et al., 1996; Yamane et al., 1991). RhoBTB, which does not undergo any known post-translational modifications, contains two BTB domains C-terminal of the GTPase domain, and does not terminate with a CAAX motif. Miro contains two EF-hand (EFH) motifs and one additional GTPase domain that are C-terminal of the Rho GTPase-like domain, and does not terminate with a CAAX motif. (B) A summary of expression patterns, regulated expression and post-translational modifications of the Rho-family proteins. The post-translational modifications that have not been experimentally verified are marked with a `?'. Abbreviations: Hp, hematopoietic; Br, brain; He, heart; Pl, placenta; Pa, pancreas; Sm, skeletal muscle; Lu, lung; Li, liver; Sp, spleen; Te, testis.