CK-1, a putative chemokine of rainbow trout (Oncorhynchus mykiss)

Chemokines are small inducible proteins that direct the migration of leukoc ytes. While chemokines are well characterised in mammals, they have yet to be identified in fish. We have isolated a cDNA clone from rainbow trout (On corhynchus mykiss) which encodes a protein (CK-1) having structural feature s typical of chemokines. Amino-acid residues that define the beta-chemokine s oi mammals are conserved in CK-1, including the paired cysteine motif, CC . Further similarities are shared with the C6 subfamily of beta-chemokines. In contrast, the organisation of the CK-I gene is closer to that of mammal ian alpha-chemokine genes than beta-chemokine genes. The CK-I gene is prese nt in all four salmonid species examined and the nucleotide sequences of th e exons are highly conserved. CK-I has characteristics in common with mamma lian alpha and beta-chemokine genes, suggesting that this salmonid chemokin e gene preserves traits once present in the ancestral chemokine gene from w hich modern mammalian chemokine genes evolved.