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Traffic. 2012 Feb;13(2):292-304. doi: 10.1111/j.1600-0854.2011.01308.x. Epub 2011 Nov 29.

Molecular dissection of novel trafficking and processing of the Toxoplasma gondii rhoptry metalloprotease toxolysin-1.

Author information

1
Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095-1489, USA.

Abstract

Toxoplasma gondii utilizes specialized secretory organelles called rhoptries to invade and hijack its host cell. Many rhoptry proteins are proteolytically processed at a highly conserved SΦXE site to remove organellar targeting sequences that may also affect protein activity. We have studied the trafficking and biogenesis of a secreted rhoptry metalloprotease with homology to insulysin that we named toxolysin-1 (TLN1). Through genetic ablation and molecular dissection of TLN1, we have identified the smallest rhoptry targeting domain yet reported and expanded the consensus sequence of the rhoptry pro-domain cleavage site. In addition to removal of its pro-domain, TLN1 undergoes a C-terminal cleavage event that occurs at a processing site not previously seen in Toxoplasma rhoptry proteins. While pro-domain cleavage occurs in the nascent rhoptries, processing of the C-terminal region precedes commitment to rhoptry targeting, suggesting that it is mediated by a different maturase, and we have identified residues critical for proteolysis. We have additionally shown that both pieces of TLN1 associate in a detergent-resistant complex, formation of which is necessary for trafficking of the C-terminal portion to the rhoptries. Together, these studies reveal novel processing and trafficking events that are present in the protein constituents of this unusual secretory organelle.

PMID:
22035499
PMCID:
PMC3375832
DOI:
10.1111/j.1600-0854.2011.01308.x
[Indexed for MEDLINE]
Free PMC Article

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