A novel C1q family member with fucose-binding activity from surfperch, Neoditrema ransonnetii (Perciformes, Embiotocidae)

The C1q family is a growing group of proteins with a globular C1q domain in the C-terminal region. We purified a new member of this family with L-fucose-binding activity from the plasma of surfperch, Neoditrema ransonnetii through L-fucose-affinity chromatography and anion-exchange chromatography. N-terminal amino acid sequencing followed by cDNA sequencing revealed that the protein was composed of 212 amino acids including a signal peptide of 20 amino acids. The gene expression analysis by RT-PCR showed that the gene was transcribed in the liver, stomach and intestine. The hepatic gene expression was up-regulated within 3 h of an intraperitoneal injection of formalin-killed Edwardsiella tarda. A phylogenetic analysis of gC1q domains placed the 23 kDa protein in the same cluster as other fish non-complement C1q-like proteins including a precerebellin-like protein of rainbow trout and ovary-specific protein of crucian carp. Interestingly, sialic acid-binding lectins of mollusca were located on the neighboring branch. Though the lectin activity has yet to be ascribed to the gC1q domain, these findings, together with former findings on lectin activity of lamprey and human C1q, indicate that sugar-binding activity is relatively common among the C1q family.