Scientists at Washington University School of Medicine in St. Louis have identified a protein made by the malaria parasite that is essential to its ability to take over human red blood cells.
Malaria, which is spread by mosquito bites, kills between 1 million and 3 million people annually in Third World countries. Death results from damage to red blood cells and clogging of the capillaries that feed the brain and other organs.
"The malaria parasite seizes control of and remodels the red blood cell by secreting hundreds of proteins once it's inside," says Dan Goldberg, M.D., Ph.D., professor of medicine and of molecular microbiology and a Howard Hughes Medical Institute Investigator. "But without this protein, plasmepsin V, those other proteins can't get out of the parasite into the blood cell, and the infectious process stops."
The closest equivalent to plasmepsin V in humans is a protein called beta secretase, but it's only distantly related. The significant differences between the malarial protein and its closest human relative may mean scientists will be able use drugs to disable plasmepsin V with little worry of adverse side effects on human biology, according to Goldberg.
The results are reported in Nature.
Goldberg had studied plasmepsin V previously and knew it was a malarial protease, or an enzyme that cuts other proteins. When another lab showed that proteins important to the infectious process were being clipped in a part of the parasite where Goldberg knew plasmepsin V was active, he and his colleagues wondered whether it was doing the clipping.