Microneme protein 5 regulates the activity of Toxoplasma subtilisin 1 by mimicking a subtilisin prodomain.
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 multistep 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. Here, 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 50-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.
Division of Molecular Biosciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.
Savvas
S
Saouros
Zhicheng
Z
Dou
Maud
M
Henry
Jan
J
Marchant
Vern B
VB
Carruthers
Stephen
S
Matthews
D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D020836:Protein Structure, Quaternary; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020860:Subtilisin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014122:Toxoplasma / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D015815:Cell Adhesion Molecules; D046912:Multiprotein Complexes; D015800:Protozoan Proteins; D020860:Subtilisin