Molecular cloning of a novel bactericidal permeability-increasing protein/lipopolysaccharide-binding protein (BPI/LBP) from common carp Cyprinus carpio L. and its expression.

A novel bactericidal permeability-increasing protein/lipopolysaccharide (LPS)-binding protein (BPI/LBP) was isolated from common carp Cyprinus carpio L. by EST analysis. This gene showed structural similarity with BPI/LBP gene in mammals. The isolated gene was composed of 1638 bp, which translated to a protein of 473 amino acid residues. The predicted signal peptide was 18 amino acid residues and the LPS-binding domain is conserved in this sequence consisted of residues 57-121 amino acid residues. This LPS-binding domain had high identity (76.9%) to that of rainbow trout LBP/BPI-2. Phylogenetic analysis showed that carp BPI/LBP was similar to BPI or LBP of lipid-interactive protein family in mammals. Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed that carp BPI/LBP gene was expressed in normal liver, head kidney, spleen, intestine, gill, heart and brain. Liver and head kidney stimulated with LPS (10 microg/ml) for 3, 6, 12, 24 and 48 h expressed carp BPI/LBP gene at all stimulation time periods. Expression level of liver was higher than that of head kidney and high expressions in each tissues was recorded at 3h post-LPS stimulation. After 3h, BPI/LBP gene expression level was gradually become less in the stimulated times.