Molecular characterization of a thrombospondin-related anonymous protein homologue in Neospora caninum

Mol Biochem Parasitol. 2000 Mar 15;107(1):33-43. doi: 10.1016/s0166-6851(99)00228-5.


Thrombospondin-related anonymous protein (TRAP) family members participate in attachment and invasion of host cells by apicomplexan parasites. A TRAP homologue in Neospora caninum strain Nc-1 (NcMIC2) was cloned, sequenced and found to be 61% identical (75% similar) at the amino acid level to Toxoplasma gondii MIC2 (TgMIC2). Similar to TgMIC2, the predicted amino acid sequence of NcMIC2 contains one integrin-like domain (I or A domain), five thrombospondin (TSP) repeats, a putative transmembrane spanning region and intracellular C-terminus, and was localized to micronemes by cryo-immunoelectron microscopy. The secretion of NcMIC2 was temperature dependent and was induced at or above 25 degrees C. The secreted form of NcMIC2 released into the medium was found to be proteolytically processed such that it lacked the C-terminal domain. Secretion of NcMIC2 was regulated by calcium, since several agents which raise intracellular calcium levels were shown to promote NcMIC2 secretion and chelation of [Ca(2+)](i) abrogated release. As a member of the growing family of apicomplexan TRAP proteins, NcMIC2 may play an important role in attachment and invasion by N. caninum into host cells.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • DNA, Protozoan / genetics
  • Molecular Sequence Data
  • Neospora / chemistry*
  • Neospora / genetics
  • Peptide Fragments / genetics
  • Protozoan Proteins / chemistry*
  • Protozoan Proteins / genetics
  • Sequence Homology, Amino Acid*
  • Temperature
  • Thrombospondins / chemistry*
  • Toxoplasma / genetics


  • DNA, Protozoan
  • Peptide Fragments
  • Protozoan Proteins
  • Thrombospondins
  • thrombospondin-related adhesive protein, protozoan

Associated data

  • GENBANK/AF061273