The novel coccidian micronemal protein MIC11 undergoes proteolytic maturation by sequential cleavage to remove an internal propeptide.
Host cell invasion is a key step in the life cycle of the intracellular parasite Toxoplasma gondii, the causative agent of toxoplasmosis. Attachment and invasion by this parasite is dependent on secretion of proteins from the micronemes, cigar-shaped organelles found in the apical end of the parasite. Although many of these proteins contain adhesive motifs suggestive of a role in parasite attachment, a growing subset of microneme proteins (MICs) do not possess adhesive sequences implying that they have alternative roles. We have identified a novel 16 kDa microneme protein, TgMIC11, that is conserved among several coccidian parasites. As it traffics through the secretory system, TgMIC11 is modified by two successive proteolytic events to remove an internal propeptide, resulting in the mature protein that consists of an alpha-chain and beta-chain tethered by a single disulfide bond. Dual staining immunofluorescence confirmed that TgMIC11 localises to the apical micronemes and, like other micronemal proteins, it is also secreted in a calcium dependent manner. This is the first microneme protein characterised to date in the phylum Apicomplexa that possesses this unique structure and undergoes maturation by removal of an internal propeptide.
W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD 21205, USA.
Jill M
JM
Harper
Xing W
XW
Zhou
Viviana
V
Pszenny
Björn F C
BF
Kafsack
Vern B
VB
Carruthers
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000037:antagonists & inhibitors; D015815:Cell Adhesion Molecules / Q000032:analysis / Q000235:genetics*; D002614:Chelating Agents / Q000494:pharmacology; D018076:DNA, Complementary / Q000235:genetics; D016054:DNA, Protozoan / Q000235:genetics; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D013058:Mass Spectrometry; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000032:analysis / Q000235:genetics*; D017422:Sequence Analysis, DNA; D014122:Toxoplasma / Q000737:chemistry / Q000187:drug effects / Q000235:genetics*
D015815:Cell Adhesion Molecules; D002614:Chelating Agents; D018076:DNA, Complementary; D016054:DNA, Protozoan; C105877:MIC1 protein, Toxoplasma gondii; D015800:Protozoan Proteins; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D002118:Calcium