Abstract
The malaria parasite Plasmodium falciparum degrades host cell hemoglobin within an acidic food vacuole. The metalloprotease falcilysin has previously been identified as an important component of this catabolic process. Using random peptide substrate analysis, we confirm that recombinant falcilysin is highly active at acidic pH, consistent with its role in hemoglobin degradation. Unexpectedly, the enzyme is also robustly active at neutral pH, but with a substantially different substrate specificity. Imaging studies confirm the location of falcilysin in the food vacuole and reveal association with vesicular structures elsewhere within the parasite. These data suggest that falcilysin may have an expanded role beyond globin catabolism and may function as two different proteases in its two locations.
Highlights
The malaria parasite Plasmodium falciparum degrades host cell hemoglobin within an acidic food vacuole
We cannot be sure of the identity of these membranes; there are morphologic similarities to endoplasmic reticulum, yet we observed minimal overlap in the distribution of the ER marker, BiP, and FLN
FLN staining was confined to the parasite body, because it is internal to the signal of LWL-1, a resident protein of the parasitophorous vacuolar membrane that delimits the parasite
Summary
The malaria parasite Plasmodium falciparum degrades host cell hemoglobin within an acidic food vacuole. Using random peptide substrate analysis, we confirm that recombinant falcilysin is highly active at acidic pH, consistent with its role in hemoglobin degradation. Imaging studies confirm the location of falcilysin in the food vacuole and reveal association with vesicular structures elsewhere within the parasite. These data suggest that falcilysin may have an expanded role beyond globin catabolism and may function as two different proteases in its two locations. Immunolocalization studies reveal a second location for FLN, outside of the acidic food vacuole These data point to the possibility of an expanded role for this protease in Plasmodium falciparum biology
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