Representative multiple sequence alignment of GPCR clusters. GPCR sequences of ET1R_Hum, ETAR_Hum, ETBR_Hum, ETB2_Hum, GRPR_Hum, NMBR_Hum, BRS3_Hum, GP37_Hum, Q8TDV0_Hum, Q9V858_Dro and Q9V9K3_Dro belonging to cluster 4 were aligned with ClustalX. Sequence region comprising of TMH-1 to TMH-7 alone were considered for the analysis (Alignment was modified by deleting the extremely variable amino termini upstream of the first transmembrane helix and carboxyl termini downstream of the seventh transmembrane helix). Identical amino-acid residues in all aligned sequences are shaded in black and similar residues in gray and consensus residues are indicated below. Transmembrane helices (TMH) identified by the HMMTOP program are indicated.