Molecular characterization of complement factor I reveals constitutive expression in channel catfish

Jason W. Abernathy, Jianguo Lu, Hong Liu, Huseyin Kucuktas, Zhanjiang Liu

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


The complement system in vertebrates plays a crucial role in immune defense via recognition and removal of pathogens. Complement is tightly regulated by a group of both soluble and cell-associated proteins. Complement factor I is a soluble serine protease that regulates multiple pathways in complement activation. In this work, a complement factor I transcript was isolated and sequenced from channel catfish (Ictalurus punctatus) liver after screening expressed sequence tags. The full-length cDNA is comprised of 2284 bp in length, encoding a polypeptide of 668 amino acids. The complement factor I protein was found to be well conserved, with similar domain structures and architecture from fish to mammals. The catfish complement factor I exists as a single-copied gene in the catfish genome. Expression analysis revealed that the catfish complement factor I is constitutively expressed in all tissues and leukocyte cell lines tested, indicating its importance as a regulatory enzyme throughout channel catfish. While expression of complement factor I is often found to be in the liver in mammals, it is constitutively expressed in channel catfish and carp throughout in various tissues and organs.

Original languageEnglish (US)
Pages (from-to)529-534
Number of pages6
JournalFish and Shellfish Immunology
Issue number3
StatePublished - Sep 2009
Externally publishedYes


  • Catfish
  • Complement
  • Complement factor I
  • Fish
  • Immunity
  • Innate immunity

ASJC Scopus subject areas

  • Environmental Chemistry
  • Aquatic Science


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