Molecular cloning, characterization and expression analysis of natural resistance associated macrophage protein (Nramp) cDNA from turbot (Scophthalmus maximus)

Nramp (natural resistance associated macrophage protein) has been identified as one of the major candidate genes for controlling natural resistance and/or susceptibility to intracellular pathogens in vertebrates. However, few reports are available about the structure and function of Nramp in teleost. We have recently isolated the cDNA encoding Nramp from turbot (Scophthalmus maximus). The full-length cDNA of the Nramp is 2584 bp in length, including 69 bp 5'terminal UTR, 850 bp 3'terminal UTR and 1665 bp open reading frame for a protein with 554 amino acid residues (Genbank accession number: DQ263240). Comparison of amino acid sequence indicated that turbot Nramp consists of 12 transmembrane regions (TM) domains. A consensus transport motif (CTM) containing 20 residues was observed between transmembrane domains 8 and 9. The deduced amino acid sequence of turbot Nramp exhibited between 60 and 92% homology with 13 other vertebrate Nramp sequences. Nramp transcripts were found to be highly abundant in head kidney, kidney and spleen, abundant in intestine and gill, less abundant in liver, brain, heart and gonad, least in muscle and skin. The level of Nramp mRNA in embryos gradually increases during embryogenesis from blastula stage to fry stage. Challenge of turbot with pathogenic bacteria, Vibrio anguillarum, elevated Nramp mRNA levels in liver and spleen. The Nramp transcripts were detected in turbot embryonic cell line (TEC). Challenge of the TEC cell cultures with pathogenic bacteria, V anguillarum, significantly elevated Nramp mRNA levels in TEC cell cultures. (c) 2006 Elsevier Inc. All rights reserved.