Gene Ontology annotation through association of InterPro records with GO terms
A molecular marker of artemisinin-resistant Plasmodium falciparum malaria.
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Long-term artemisinin selection of an African parasite line fixed the PF3D7_1343700 M476I substitution, which accompanied a rise in ring-stage survival, and propeller alleles in Cambodian isolates correlate with resistance in vitro and in vivo.
"These data indicate that the PF3D7_1343700 M476I mutation increased the resistance of F32-Tanzania to DHA in the RSA0–3h."
Drug resistance. K13-propeller mutations confer artemisinin resistance in Plasmodium falciparum clinical isolates.
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Zinc-finger-nuclease editing of the K13 locus in Cambodian isolates shows that propeller mutations are causal for ring-stage survival, since removing them drops survival and inserting them raises it.
"With isolates from Cambodia, where resistance first emerged, survival rates decreased from 13 to 49% to 0.3 to 2.4% after the removal of K13 mutations."
A molecular mechanism of artemisinin resistance in Plasmodium falciparum malaria.
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PfPI3K co-immunoprecipitates with wild-type Kelch13 and binding is reduced by the C580Y substitution, which the authors read as loss of substrate-adaptor function leading to elevated PfPI3K and PI3P.
"Further analysis revealed that immunopurified (IP) PfPI3K was bound to PfKelch13WT and this was reduced by the C580Y mutation (Fig. 2e)."
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The substrate-adaptor interpretation is explicitly an argument from the mammalian orthologue rather than a demonstration of a parasite cullin-RING ligase.
"The mammalian orthologue of PfKelch13 functions is a substrate adapter for an E3 ubiquitin ligase"
A Kelch13-defined endocytosis pathway mediates artemisinin resistance in malaria parasites.
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Kelch13 and seven further proteins of the Kelch13-defined compartment are required for endocytosis of host haemoglobin, and their inactivation confers artemisinin resistance because less haemoglobin-derived haem is available to activate the drug.
"Functional analysis showed that these proteins are required for endocytosis of hemoglobin from the host cell. Parasites with inactivated Kelch13 or a resistance-conferring Kelch13 mutation displayed reduced hemoglobin endocytosis."
Insights into the intracellular localization, protein associations and artemisinin resistance properties of Plasmodium falciparum K13.
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Monoclonal-antibody imaging places K13 at the endoplasmic reticulum, on Rab-positive vesicles and at sites adjacent to cytostomes, the structures that carry endocytosed host haemoglobin to the digestive vacuole.
"we localize K13 to the parasite endoplasmic reticulum, Rab-positive vesicles, and sites adjacent to cytostomes."
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Co-immunoprecipitation with K13 monoclonal antibodies recovered ER residents, mitochondrial proteins and Rab GTPases, but no cullin-RING ligase components.
"Immunoprecipitation data generated with K13-specific monoclonal antibodies identify multiple putative K13-associated proteins, including endoplasmic reticulum-resident molecules, mitochondrial proteins, and Rab GTPases, in both K13 mutant and wild-type isogenic lines."
Plasmodium falciparum Kelch13 and its artemisinin-resistant mutants assemble as hexamers in solution: a SAXS data-driven modelling study.
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Solution scattering shows full-length PfKelch13 forms a stable hexamer with P6 symmetry driven by N-terminal interactions, complementing the two available crystal structures of the BTB-propeller region as tight dimers.
"PfKelch13 forms a stable hexamer in P6 symmetry, (b) interactions of the N-termini drive the hexameric assembly, and (c) the six KRP domains project independently in space, forming a cauldron-like architecture."
The Kelch13 compartment contains highly divergent vesicle trafficking proteins in malaria parasites.
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Proteins of the Kelch13 compartment that affect endocytosis or artemisinin susceptibility are enriched in vesicle-trafficking and endocytosis domains, while a second group at the same site lacks them and affects neither, indicating a highly taxon-adapted endocytic machinery.
"vesicle trafficking and endocytosis domains were frequent in proteins involved in resistance or endocytosis (or both), comprising one group of K13 compartment proteins."
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Host haemoglobin reaches the food vacuole by uptake at cytostomal invaginations of the parasite plasma membrane followed by vesicular transport.
"Hemoglobin trafficking to the parasite food vacuole is believed to be initiated at membrane invaginations called cytostomes [30,42,48,49] followed by vesicular transport from the parasite plasma membrane (PPM) to the food vacuole [42,50], likely in an actin-myosin motor dependent manner [48,51–53]."
Impact of different mutations on Kelch13 protein levels, ART resistance, and fitness cost in Plasmodium falciparum parasites.
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Across isogenic lines, Kelch13 protein amount correlates with artemisinin resistance and with fitness cost, and titration of Kelch13 and KIC7 shows resistance is set by the rate of endocytosis these proteins support.
"Titration of K13 and KIC7 indicated that the cellular levels of these proteins determined resistance through the rate of endocytosis."
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Kelch13 and its compartment neighbours, including UBP1, function in endocytosis of host cell cytosol.
"K13 and its compartment neighbors (KICs), including UBP1, are involved in endocytosis of host cell cytosol."
UniProtKB entry Q8IDQ2 (Kelch protein K13, PF3D7_1343700)
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The entry records a BTB domain at residues 350-452, six Kelch repeats, a coiled coil and a disordered N-terminal region, and the PDB entry 4ZGC covering residues 338-726.
"DOMAIN 350..452"