Cloning of two chemokine receptor homologs (CXC-R4 and CC-R7) in rainbow trout Oncorhynchus mykiss

Two rainbow trout chemokine receptors have been sequenced, with homology to CXC‐R4 and CC‐R7 molecules. The CXC‐R4 sequence consisted of 1681 nucleotides, which translated into a mature protein of 357 amino acids, with 80.7% similarity to human CXC‐R4. The CC‐R7 sequence consisted of 2287 nucleotides, which translated into a 368‐amino acid mature protein with 64.5% similarity to human CC‐R7. Both sequences contained seven hydrophobic regions, representing the seven transmembrane domains (TM) typical of G‐protein‐coupled receptors. Extracellular cysteines, transmembrane prolines, and the DRY motif immediately following TM3 were conserved. Phylogenetic tree analysis revealed a tight clustering of trout CXC‐R4 with CXC‐R3‐5 genes. Trout CC‐R7 clustered with CC‐R6‐7 and CXC‐R1‐2. Reverse transcriptase‐polymerase chain reaction analysis demonstrated a wide tissue distribution of CXC‐R4 and CC‐R7 message in trout, being present in head‐kidney leukocytes, blood, gill, brain, spleen, and liver. J. Leukoc. Biol. 65: 684–690; 1999.