The Toxoplasma homolog of Plasmodium apical membrane antigen-1 (AMA-1) is a microneme protein secreted in response to elevated intracellular calcium levels

Carolyn G. Donahue, Vern B. Carruthers, Stacey D. Gilk, Gary E. Ward

Research output: Contribution to journalArticlepeer-review

92 Scopus citations

Abstract

A monoclonal antibody (MAb) has been generated against a novel 63 kDa surface/apical antigen of Toxoplasma gondii tachyzoites which is identified here as TgAMA-1, the Toxoplasma homolog of Plasmodium apical membrane antigen-1 (AMA-1). Sequence analysis, phase partitioning in Triton X-114, and labeling of TgAMA-1 with iodonaphthalene azide all suggest that TgAMA-1 is a type I transmembrane protein. There is a high degree of sequence similarity between TgAMA-1 and Plasmodium AMA-1, most notably in the position of conserved cysteine residues within the protein's predicted extracellular domain. In contrast to full length Plasmodium AMA-1, which has previously been localized to the rhoptries, it is shown here by immunofluorescence and immunoelectron microscopy that intracellular TgAMA-1 is found in the micronemes. A 53 kDa N-terminal proteolytic fragment of TgAMA-1 is constitutively secreted from the parasite at 37°C. As is the case with other microneme proteins, the proteolytic processing and secretion of TgAMA-1 is dramatically enhanced in response to treatments which increase intracellular calcium levels. Copyright (C) 2000 Elsevier Science B.V.

Original languageEnglish (US)
Pages (from-to)15-30
Number of pages16
JournalMolecular and Biochemical Parasitology
Volume111
Issue number1
DOIs
StatePublished - 2000
Externally publishedYes

Keywords

  • Apical membrane antigen-1
  • Microneme
  • Plasmodium
  • Secretion
  • Toxoplasma

ASJC Scopus subject areas

  • Parasitology
  • Molecular Biology

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