Molecular cloning and characterization of novel ficolins from Xenopus laevis

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• 作者：Yuji Kakinuma ; Yuichi Endo ; Minoru Takahashi ; Munehiro Nakata ; Misao Matsushita ; Seiichi Takenoshita and Teizo Fujita
• 刊名：Immunogenetics
• 出版年：2003
• 出版时间：April 2003
• 年：2003
• 卷：55
• 期：1
• 页码：29-37
• 全文大小：382 KB
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Biomedicine
  Immunology
  Allergology
  Cell Biology
  
• 出版者：Springer Berlin / Heidelberg
• ISSN：1432-1211

文摘

Ficolins are proteins characterized by the presence of collagen- and fibrinogen-like domains. Two of three human ficolins, L-ficolin and H-ficolin, are serum lectins and are thought to play crucial roles in host defense through opsonization and complement activation. To elucidate the evolution of ficolins and the primordial complement lectin pathway, we cloned four ficolin cDNAs from Xenopus laevis, termed Xenopus ficolin (XeFCN) 1, 2, 3 and 4. The deduced amino acid sequences of the four ficolins revealed the conserved collagen- and fibrinogen-like domains. The full sequences of the four ficolins showed a 42-56% identity to human ficolins, and 60-83% between one another. Northern blots showed that XeFCN1 was expressed mainly in liver, spleen and heart, and XeFCN2 and XeFCN4 mainly in peripheral blood leukocytes, lung and spleen. We isolated ficolin proteins from Xenopus serum by affinity chromatography on N-acetylglucosamine-agarose, followed by ion-exchange chromatography. The final eluate showed polymeric bands composed of two components of 37 and 40 kDa. The N-terminal amino acid sequences and treatment with endoglycosidase F showed that the two bands are the same XeFCN1 protein with different masses of N-linked sugar. The polymeric form of the two types of XeFCN1 specifically recognized GlcNAc and GalNAc residues. These results suggest that like human L-ficolin, XeFCN1 functions in the circulation through its lectin activity.