Characterisation of a novel Kunitz-type molecule from the trematode Fasciola hepatica

S. Esther Bozas, Michael Panaccio, Jenette Creaney, Marina Dosen, James C Parsons, George V. Vlasuk, Ian D. Walker, Terry W. Spithill

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Abstract

A low molecular mass monomeric protein termed Fh-KTM (Fasciola hepatica Kunitz-type molecule) was isolated from the trematode Fasciola hepatica. Fh-KTM is a single polypeptide of 58 amino acids and a Mr of 6751. The complete amino acid sequence of Fh-KTM was determined and revealed significant similarity to the Kunitz-type (BPTI) family of proteinase inhibitors. Several polymorphisms were observed suggesting that more than one Fh-KTM molecule may be expressed by this parasite. Modified proline residues were shown to occur at all four positions in this protein as 3-hydroxy derivatives. This is the first report of 3-hydroxyproline residues in a Kunitz-type molecule. Indirect immunofluorescence and immunogold labelling revealed that Fh-KTM is an abundant molecule within the parasite localised to the gut, the parenchymal tissue and the tegument of adult F. hepatica. Serine protease inhibition assays revealed that Fh-KTM exhibited little or no inhibition against chymotrypsin, kallikrein, urokinase or key serine proteases of the blood coagulation pathways. However, Fh-KTM was able to inhibit trypsin even though the P1 reactive amino acid of Fh-KTM was a leucine residue.

Original languageEnglish
Pages (from-to)19-29
Number of pages11
JournalMolecular and Biochemical Parasitology
Volume74
Issue number1
DOIs
Publication statusPublished - 1995
Externally publishedYes

Keywords

  • 3-Hydroxy proline
  • Fasciola hepatica
  • Immunolocalisation
  • Kunitz

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