Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.1 (chymotrypsin)
 10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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

Pregnancy-associated malaria (PAM) is characterized by the placental sequestration of Plasmodium falciparum-infected erythrocytes (IEs) with the ability to bind to chondroitin sulfate A (CSA). VAR2CSA is a leading candidate for a pregnancy malaria vaccine, but its large size ( approximately 350 kDa) and extensive polymorphism may pose a challenge to vaccine development. In this study, rabbits were immunized with individual VAR2CSA Duffy binding-like (DBL) domains expressed in Pichia pastoris or var2csa plasmid DNA and sera were screened on different CSA-binding parasite lines. Rabbit antibodies to three recombinant proteins (DBL1, DBL3, and DBL6) and four plasmid DNAs (DBL1, DBL3, DBL5, and DBL6) reacted with homologous FCR3-CSA IEs. By comparison, antibodies to the DBL4 domain were unable to react with native VAR2CSA protein unless it was first partially proteolyzed with trypsin or chymotrypsin. To investigate the antigenic relationship of geographically diverse CSA-binding isolates, rabbit immune sera were screened on four heterologous CSA-binding lines from different continental origins. Antibodies did not target conserved epitopes exposed in all VAR2CSA alleles; however, antisera to several DBL domains cross-reacted on parasite isolates that had polymorphic loops in common with the homologous immunogen. This study demonstrates that VAR2CSA contains common polymorphic epitopes that are shared between geographically diverse CSA-binding lines.
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PMID:Evidence for globally shared, cross-reacting polymorphic epitopes in the pregnancy-associated malaria vaccine candidate VAR2CSA. 1825 Jan 77

The ligands that pathogens use to invade their target cells have often proven to be good targets for vaccine development. However, Plasmodium falciparum has redundant ligands that mediate invasion of erythrocytes. The first requirement for the development of a successful ligand-blocking malaria vaccine is the demonstration that antibodies induced to each ligand can block the erythrocyte invasion of parasites with polymorphic sequences. Because of P. falciparum's redundancy in erythrocyte invasion, each ligand needs to be studied under artificial conditions in which parasite invasion is restricted in its use of alternative pathways. Here we investigate the role of erythrocyte-binding antigen 175 (EBA-175), a parasite ligand that binds to sialic acid on glycophorin A, in the invasion of erythrocytes by 10 P. falciparum clones under conditions in which invasion is partially limited to the EBA-175-glycophorin A pathway, using chymotrypsin-treated erythrocytes. We show that the ability to invade erythrocytes for both sialic acid-independent and sialic acid-dependent pathways requires the EBA-175-glycophorin A pathway for erythrocyte invasion. Importantly, antibodies against region II of EBA-175 from the 3D7 clone blocked invasion of chymotrypsin-treated erythrocytes by >50% by all parasite clones studied, including those with multiple different mutations described in the literature. The one exception was FCR3, which had a similar sequence to 3D7 but only 30% inhibition of invasion of chymotrypsin-treated erythrocytes, indicating alternative pathways for invasion of chymotrypsin-treated erythrocytes. Our findings suggest that antibodies to region II of EBA-175, as one component of a ligand-blocking malaria vaccine, are largely unaffected by polymorphism in EBA-175.
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PMID:Evidence for erythrocyte-binding antigen 175 as a component of a ligand-blocking blood-stage malaria vaccine. 2150 13

The malaria parasite Plasmodium falciparum invades human erythrocytes through multiple pathways utilizing several ligand-receptor interactions. These interactions are broadly classified in two groups according to their dependency on sialic acid residues. Here, we focus on the sialic acid-dependent pathway by using purified glycophorins and red blood cells (RBCs) to screen a cDNA phage display library derived from P. falciparum FCR3 strain, a sialic acid-dependent strain. This screen identified several parasite proteins including the erythrocyte-binding ligand-1, EBL-1. The phage cDNA insert encoded the 69-amino acid peptide, termed F2i, which is located within the F2 region of the DBL domain, designated here as D2, of EBL-1. Recombinant D2 and F2i polypeptides bound to purified glycophorins and RBCs, and the F2i peptide was found to interfere with binding of D2 domain to its receptor. Both D2 and F2i polypeptides bound to trypsin-treated but not neuraminidase or chymotrypsin-treated erythrocytes, consistent with known glycophorin B resistance to trypsin, and neither the D2 nor F2i polypeptide bound to glycophorin B-deficient erythrocytes. Importantly, purified D2 and F2i polypeptides partially inhibited merozoite reinvasion in human erythrocytes. Our results show that the host erythrocyte receptor glycophorin B directly interacts with the DBL domain of parasite EBL-1, and the core binding site is contained within the 69 amino acid F2i region (residues 601-669) of the DBL domain. Together, these findings suggest that a recombinant F2i peptide with stabilized structure could provide a protective function at blood stage infection and represents a valuable addition to a multi-subunit vaccine against malaria.
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PMID:Identification of a specific region of Plasmodium falciparum EBL-1 that binds to host receptor glycophorin B and inhibits merozoite invasion in human red blood cells. 2227 81