Abstract:
Pentraxins are a family of evolutionary conserved proteins that contains two main members, namely creactive proteins (CRPs) and serum amyloid P (SAP), which are involved in acute phase responses in
animals. In this study, a cDNA sequence of a CRP-like molecule was identified from a previously constructed black rockfish cDNA database (RfCRP) and subsequently characterized at its molecular level. The
complete coding region of RfCRP is 672 bp in length, and encodes a protein containing 224 amino acids
with a predicted molecular mass of 25.19 kDa. Analysis of its derived amino acid sequence enabled
typical features of pentraxin family members to be identified, including the pentraxin family signature in
RfCRP. Results from multiple sequence alignment suggest the conservation of functionally important
residues in RfCRP. According to the phylogenetic reconstruction that was generated using different
pentraxin counterparts from different taxa, RfCRP shares a common vertebrate ancestral origin and most
closely clusters with marine teleostan CRP. Furthermore, recombinant RfCRP demonstrated Ca2þdependent agglutination activity against Escherichia coli, which could be completely inhibited in the
presence of carbohydrate based ligands. Moreover, recombinant RfCRP also exhibited anti-bacterial activity against both E. coli and Streptococcus iniae. In addition, qPCR analysis indicated that RfCRP is
ubiquitously expressed in physiologically important tissues, with pronounced expression in the spleen.
After healthy fish were treated with polysaccharides or live S. iniae, basal expression of RfCRP was
significantly upregulated in spleen and head kidney tissues. Collectively, our results suggest that RfCRP
may be important in host anti-bacterial defense, and it might potentially participate in the acute phase of
infection.
