Toxoplasma Gondii Toxolysin 4 Is an Extensively Processed Putative Metalloproteinase Secreted From Micronemes

Mol Biochem Parasitol. 2011 May;177(1):49-56. doi: 10.1016/j.molbiopara.2011.01.009. Epub 2011 Jan 26.


Proteases play central roles in cell invasion by Toxoplasma gondii and other apicomplexan parasites. Herein we report the cloning and characterization of a novel secretory putative metalloproteinase, Toxolysin 4 (TLN4). T. gondii tachyzoites store TLN4 in the micronemes and secrete it in response to elevated calcium, suggesting a possible role in cell invasion. TLN4 is initially synthesized as a large (∼260 kDa) precursor, which is extensively processed into multiple proteolytic fragments within the parasite secretory system. At least some of these proteolytic fragments remain associated in a large molecular complex. Whereas precomplementation with the TLN4 cDNA allowed disruption of the TLN4 gene, multiple attempts to directly knockout TLN4 without precomplementation failed. TLN4 knockout parasites were detected by PCR in transfected populations but were lost from the cultures during drug selection and growth suggesting that TLN4 contributes to parasite fitness.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Extracellular Space / chemistry
  • Extracellular Space / enzymology*
  • Extracellular Space / genetics
  • Metalloproteases / chemistry
  • Metalloproteases / genetics
  • Metalloproteases / metabolism*
  • Molecular Sequence Data
  • Organelles / chemistry
  • Organelles / enzymology*
  • Organelles / genetics
  • Protein Processing, Post-Translational
  • Protein Structure, Tertiary
  • Protein Transport
  • Protozoan Proteins / chemistry
  • Protozoan Proteins / genetics
  • Protozoan Proteins / metabolism*
  • Toxoplasma / chemistry
  • Toxoplasma / enzymology*
  • Toxoplasma / genetics


  • Protozoan Proteins
  • Metalloproteases

Associated data

  • GENBANK/HQ848740