Table 1.

ECL2 ‘hot-spot’ residues of family A GPCRs interacting with bound ligand

		ECL2 residues interacting with ligand
Receptor	Ligand	C − 3	C − 2	C − 1	C0	C + 1	C + 2	C + 3	C + 4
rhodopsin	11-cis-retinal			Ser186		Gly188	Ile189		Tyr191
β1AR	cyanopindolol						Phe201		Thr203
β2AR	carazolol						Phe193
A2AR	ZM241385						Phe168	Glu169
D3R	eticlopride						Ile183
CXCR4	IT1t	Arg183		Ile185	Cys186	Asp187
CXCR4	CVX15					Asp187	Arg188		Tyr190

ECL2 residues forming interactions with the named ligand are cited by their residue number for each receptor listed (Palczewski et al., 2000; Li et al., 2004; Cherezov et al., 2007; Jaakola et al., 2008; Warne et al., 2008; Chien et al., 2010; Wu et al., 2010). ECL2 residue nomenclature (C + 1, C + 2 etc.) uses a standard nomenclature in which the ECL2 Cys forming the well-conserved disulfide bond to TM3 is designated as the reference residue C0 (see text for details).