Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To determine the ligands on erythrocytes for invasion by Plasmodium falciparum, we tested invasion into MkMk erythrocytes that lack glycophorins A and B and enzyme-treated erythrocytes by parasites that differ in their requirement for erythrocyte sialic acid. The 7G8 strain invaded MkMk erythrocytes and neuraminidase-treated normal erythrocytes with greater than 50% the efficiency of normal erythrocytes. In contrast, the Camp strain invaded MkMk erythrocytes at 20% of control and neuraminidase-treated normal erythrocytes at only 1.8% of control. Invasion of MkMk erythrocytes by 7G8 parasites was unaffected by treatment with neuraminidase but was markedly reduced by treatment with trypsin. In contrast, invasion of MkMk cells by Camp parasites was markedly reduced by neuraminidase but was unaffected by trypsin. We conclude that the 7G8 and Camp strains differ in ligand requirements for invasion and that 7G8 requires a trypsin sensitive ligand distinct from glycophorins A and B.
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PMID:Falciparum malaria parasites invade erythrocytes that lack glycophorin A and B (MkMk). Strain differences indicate receptor heterogeneity and two pathways for invasion. 330 59

A 92,000 D protein was identified associated with the membrane of host erythrocytes infected with the FCB1 Plasmodium falciparum strain from Colombia. The same protein was identified in the knob-forming Gambian (and the Malayan Camp) strain, but was not present in all the corresponding knobless strains. In the FCB1 strain as well as in the FCR3 strain the protein is synthesized during the ring-stage period. The cleavage products of the 92,000 D protein were investigated by peptide mapping following limited proteolytic digestion with Staphylococcus aureus V8 protease. The 92,000 D protein cleavage products from both the Colombian and the Gambian strains were identical. Moreover, both the proteins were sensitive to trypsin and chymotrypsin and also to treatment with neuraminidase. Enzymatic removal of the protein from the erythrocyte membrane by trypsin or chymotrypsin did not affect parasite maturation. The merozoites thus produced were fully invasive and the morphology of the knobs was unaltered. When the erythrocyte membrane was treated with trypsin before the time of synthesis of the 92,000 D protein, it was not possible to identify the protein in membranes of later stages of infected erythrocytes, indicating that the protein cannot be inserted into the membrane cytoskeleton compartment. Knobs, however, were formed more or less normally, suggesting that it is not the accumulation of this protein which products the knobs.
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PMID:The relationship to knobs of the 92,000 D protein specific for knobby strains of Plasmodium falciparum. 388 5

We have identified strain-specific antigens with Camp and St. Lucia strains of P. falciparum of Mr approximately 285,000 and approximately 260,000, respectively. These strain-specific antigens were metabolically labeled with radioactive amino acids, indicating that they were of parasite origin rather than altered host components. These proteins had the properties of a molecule exposed on the surface of infected erythrocytes (IE). First, the proteins are accessible to lactoperoxidase-catalyzed radioiodination of IE. Second, the radioiodinated proteins were cleaved by low concentrations of trypsin (0.1 microgram/ml). Third, these antigens were immunoprecipitated after addition of immune sera to intact IE. Fourth, the strain-specific immuno-precipitation of these proteins correlated with the capacity of immune sera to block cytoadherence of IE in a strain-specific fashion. Fifth, the strain-specific antigen had detergent solubility properties (i.e., insolubility in 1% Triton X-100, solubility in 5% sodium dodecyl sulfate) similar to the variant antigen of P. knowlesi, which has been proven to be a malarial protein exposed on the erythrocyte surface.
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PMID:Identification of a strain-specific malarial antigen exposed on the surface of Plasmodium falciparum-infected erythrocytes. 637 9