TABLE 2

Location of naturally occurring, loss-of-function GPCRs mutations that compromise or involve believed ER export motifs [YS amino-terminal motif; E(X)₃LL carboxyl-terminal motif], the Arg-X-Arg retention motif, the NxS/T consensus for N-glycosylation ( Tan et al., 2004 ; Dong et al., 2007 ), the AFNGT motif (present in the gonadotropin receptors that comprise the NxT consensus for glycosylation) ( Huhtaniemi and Themmen, 2005 ), the BBxxB or BBxB motifs [involved in G protein activation ( Okamoto and Nishimoto, 1992 )], the E/DRYxxI/V and N/DPxxY highly conserved motifs [involved in receptor activation and G protein coupling/recognition ( Gether and Kobilka, 1998 ; Rovati et al., 2007 )], and the predicted disulfide bridge between the ECL1 and ECL2. Mutations at sites in bold letters resulted in reported traffic-defective or plasma membrane expression-deficient mutant receptors