Chemokine and chemokine receptor sequences, such as (a) CXCR4, (b) CXCL12 and (c) CXCL8, are highly conserved throughout evolution, from jawless fish to humans. Identical amino acid residues are highlighted in green; the seven transmembrane regions of the receptors are indicated by black lines; the four conserved cysteine residues are indicated by dots above the sequences. Species abbreviations: dare, Danio rerio (zebrafish); pema, Petromyzon marinus (sea lamprey); lafl, Lampetra fluviatilis (European river lamprey). Accession numbers (from GenBank) are as follows: human CXCR4, NM_003467; zebrafish cxcr4b, NM_131834; sea lamprey cxcr4, AY178969; human CXCL12, NM_000609; zebrafish cxcl12a, NM_178307; zebrafish cxcl12b, NM_198068; human IL-8, NM_000584; river lamprey CXCL8, AJ231072.
Zlotnik et al. Genome Biology 2006 7:243 doi:10.1186/gb-2006-7-12-243