Microneme protein 5 regulates the activity of Toxoplasma subtilisin 1 by mimicking a subtilisin prodomain

J Biol Chem. 2012 Aug 15. [Epub ahead of print]

Microneme protein 5 regulates the activity of Toxoplasma subtilisin 1 by mimicking a subtilisin prodomain

Saouros S, Dou Z, Henry M, Marchant J, Carruthers VB, Matthews S.

Imperial College London, United Kingdom

Toxoplasma gondii is the model parasite of the phylum Apicomplexa, which contains obligate intracellular parasites of medical and veterinary importance. Apicomplexans invade host cells by a multi-step process involving the secretion of adhesive microneme protein (MIC) complexes. The subtilisin protease TgSUB1 trims several MICs on the parasite surface to activate gliding motility and host invasion. Although a previous study showed that expression of the secretory protein TgMIC5 suppresses TgSUB1 activity, the mechanism was unknown. Herein, we solve the three dimensional structure of TgMIC5 by Nuclear Magnetic Resonance (NMR), revealing that it mimics a subtilisin prodomain including a flexible C-terminal peptide that may insert into the subtilisin active site. We show that TgMIC5 is an almost fifty-fold more potent inhibitor of TgSUB1 activity than the small molecule inhibitor N-[N-(N-Acetyl-L-leucyl)-L-leucyl]-L-norleucine (ALLN). Moreover, we demonstrate that TgMIC5 is retained on the parasite plasma membrane via its physical interaction with the membrane anchored TgSUB1.

PMID: 22896704 [PubMed - as supplied by publisher]