A cDNA encoding Tc-MUC-5, a mucin from Toxocara canis larvae identified by expression screening.
Toxocara canis is an ascarid nematode parasite of canids. Larvae infect a wide range of accidental hosts including humans, in whom they are the aetiologic agent of visceral and ocular Larva migrans. The labile surface coat of T. canis larvae consists of a family of mucin glycoproteins termed TES-120, for which the cDNAs have recently been cloned. In this paper, we describe the identification of a novel cDNA (Tc-muc-5) encoding an apomucin by expression screening of a cDNA library with antiserum raised to T. canis excretory/secretory products, and compare the predicted Tc-MUC-5 protein with those of other T. canis mucins (Tc-MUC-1-Tc-MUC-4) that include the TES-120 surface coat glycoproteins. Tc-MUC-5 has both a larger open reading frame and a more divergent sequence than the other T. canis mucins. It contains a putative signal peptide followed by two six-cysteine (SXC) domains, an extended threonine-rich central mucin core domain and two C-terminal SXC domains. Amino acid composition analysis of secreted TES-120 glycoproteins revealed a distinct lack of lysine residues; while this finding is in agreement with the primary sequences of Tc-MUC-1-Tc-MUC-4, Tc-MUC-5 is conspicuous by its relative abundance of lysines (6.7%), suggesting that this protein is not part of the TES-120 family of surface coat proteins.
Doedens
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Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, EH9 3JT, Edinburgh, UK.
Loukas
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Maizels
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D000595:Amino Acid Sequence; D000818:Animals; D000909:Antibodies, Helminth; D001059:Apoproteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002335:Carnivora; D003001:Cloning, Molecular; D018509:DNA, Helminth / Q000235:genetics; D015723:Gene Library; D017238:Genes, Helminth; D015801:Helminth Proteins / Q000235:genetics* / Q000378:metabolism; D007814:Larva / Q000235:genetics / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009077:Mucins / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D017166:Toxocara canis / Q000235:genetics* / Q000378:metabolism
D000909:Antibodies, Helminth; D001059:Apoproteins; D018509:DNA, Helminth; D015801:Helminth Proteins; D008562:Membrane Glycoproteins; D009077:Mucins