title: The isolation, characterization and cloning of a globin-like, host-protective antigen from the excretory-secretory products of Trichostrongylus colubriformis.
abstract: An 18-kDa component from the excretory-secretory (ES) products of adults of Trichostrongylus colubriformis was isolated and characterized, and was shown to induce 60-84% protection of guinea pigs from challenge infection following a single intraperitoneal injection. Amino-terminal sequence analysis of gel-purified protein enabled oligonucleotides to be synthesized and used to screen a lambda gt10 cDNA library made from young adult worm mRNA, and to synthesize full-length clones from cDNA using the polymerase chain reaction (PCR). The full-length clones coded for a 20-kDa precursor protein of 173 amino acids which had a strongly hydrophobic leader sequence of 15 residues. The mature protein sequence of 158 amino acid residues was rich in charged amino acids (32%), including 8 oppositely charged pairs of amino acids. The protein sequence contained no half-cystine residues and no potential N-glycosylation sites. Unlike 2 other fully characterized ES components which are expressed only in the parasitic stages, mRNA coding for the 20-kDa component was present in both the parasitic and free-living stages of T. colubriformis. The parasite protein had approximately 20% identity with globins from human and from the larvae of the insect Chironomus thummi thummi. The homology included the invariant distal histidine and phenylalanine, and a number of other residues highly conserved in globins.
authors.affiliation: CSIRO Division of Biomolecular Engineering, Parkville, Victoria, Australia.
authors.forename: M J
authors.initials: MJ
authors.lastname: Frenkel
authors.forename: T A
authors.initials: TA
authors.lastname: Dopheide
authors.forename: B M
authors.initials: BM
authors.lastname: Wagland
authors.forename: C W
authors.initials: CW
authors.lastname: Ward
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000947:Antigens, Helminth / Q000235:genetics* / Q000302:isolation & purification; D001483:Base Sequence; D015152:Blotting, Northern; D003001:Cloning, Molecular; D004247:DNA / Q000302:isolation & purification; D005914:Globins / Q000235:genetics / Q000276:immunology; D006168:Guinea Pigs; D006801:Humans; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D016415:Sequence Alignment; D014254:Trichostrongylus / Q000235:genetics / Q000276:immunology*
chemical_list: D000947:Antigens, Helminth; C073167:TcAdES3 antigen; D005914:Globins; D004247:DNA