Table 2. The measured distance between selected residues in NBDs and ECLs.

Position	Residue	Measured distance (Å)
		P-gpSECO	P-gpVerapamil	ApoP-gp
NBDs	R1043-D558	18.15	20.7	35
	C427-C1070	21.8	27.8	37
TM3-TM4	G187-G226	13.9	14.5	16.2
ECL	P741-N90	18.77	28.33	32.26
	Q962-N90	11.63	10.15	8.79
	I848-N90	25.95	26.77	29.37
	P741-Y849	24.52	24.82	26
	Q962-Y849	15.35	20.35	21.58

Note:

NBD, nucleotide-binding domain; ECL, extracellular loop; P-gp, P-glycoprotein; SECO, secoisolariciresinol; ApoP-gp, empty form of P-glycoprotein without binding to any ligand; TM, transmembrane.