Author(s): Kawabata S, Tokunaga F, Kugi Y, Motoyama S, Miura Y,
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Abstract A glycoprotein (Mr = 43,000) from horseshoe crab hemocytes with antimicrobial activity against Gram-negative bacteria was purified. The internal peptide sequences coincided exactly with the deduced amino acid sequence of a cDNA clone, designated limulus factor D, which was isolated by screening a hemocyte cDNA library with an anti-human plasminogen antibody. The open reading frame codes for a precursor of factor D of 394 amino acid residues, including an NH2-terminal signal sequence. The COOH-terminal domain of factor D has significant sequence homology with the catalytic domain of mammalian serine proteases, in particular with human tissue plasminogen activator (32\% identity), except for the substitution of Ser of the active site triad to Gly. Factor D has a unique NH2-terminal domain with weak sequence homology with part of the mammalian interleukin-6 receptor alpha-chain. Factor D is likely to have an important role in host defense mechanisms.
This article was published in FEBS Lett
and referenced in Journal of Aquaculture Research & Development