Table 3. Evolution of the sodium binding site in the chemokine receptor family.

Receptors	Positions a					N b	Genomes c
	2.49	3.35	3.39	6.48	7.45		L	S	Z	H
ACKR3/CXCR7	A	N	S	W	H	2	••	•	•	•
CXCR4	A	N	S	W	H	1	•	•	•	•
CXCR5	A	N	S	W	H	1		•	•	•
CXCR3	A	N	G	W	H	10			•	•
CCR10	A	S	G	Q	R	2			•	•
CXCR2	A	N	G	W	H	7			•	•
CXCR1	A	N	G	W	H	3		••	•	•
CCR6	A	N	G	Q	H	1		•	••	•
CXCR6	A	N	S	Q	R	1		•		•
ACKR4/CCRL1	A	N	G	Q	H	3			•	•
CCR9	A	N	C	Q	H	1		•	•	•
CCR7	A	S	G	Q	R	2		•	•	•
XCR1	S	S	S	W	H	1		•	•	•
ACKR2/CCBP2/D6	S	N	G	W	H	11				•
CX3CR1	S	G	S	W	H	1			•	•
CCR8	S	G	S	W	H	1		•	•	•
CCR4	S	G	G	W	H	2				•
CCR2	S	G	G	W	H	8				•
CCR5	S	G	G	W	H	10				•
CCRL2	S	G	E	W	H	2				•
CCR1	S	G	E	W	H	11				•
CCR3	S	G	E	W	H	14				•

^a The residues at the indicated positions were obtained from the human sequences.

^b N represents the number of binding chemokines for the human receptors [1].

^c The presence of orthologs of human chemokine receptors in different genomes is based on Nomiyama’s data [3]. L: Sea lamprey (jawless fish), S: Elephant shark (cartilaginous fish), Z: zebra fish (bony fish); H: Human. Double symbols indicate two orthologs. The receptors that are specific to fish species and not present in humans are not indicated.