Isolation of carp complement factor B and formation of the C3-convertase

Miki Nakao, Makiko Nakahara, Tomoki Yano

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Complement factor B (Bf) is a key component that forms a catalytic site of C3-convertase of the alternative activation pathway. However, the functional assay and isolation method has been developed poorly for Bf in fish. We describe here a hemolytic assay method for Bf of carp (Cyprinus carpio). The assay devised from purified carp C3 and factor D (Df) is based on the action of Bf which cleaves C3 in the presence of Df. Using this assay method as a probe, carp Bf was isolated from serum, and proved to be a protein composed of a single polypeptide with a molecular mass of 93 kDa. This Bf protein was identified as a mature product of the B/C2-A1 isotype gene of carp. The C3-convertase of the alternative pathway of carp complement was assembled from purified C3, Bf and Df, and generation of C3b, the initial biologically active fragment derived from C3, was confirmed, suggesting a well conserved mechanism of the formation of the alternative pathway C3-convertase.

Original languageEnglish
Pages (from-to)101-110
Number of pages10
JournalJournal of the Faculty of Agriculture, Kyushu University
Issue number1
Publication statusPublished - Feb 2004

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Agronomy and Crop Science


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