scholarly journals Effect of polyamine depletion on macromolecular synthesis of the malarial parasite, Plasmodium falciparum, cultured in human erythrocytes

1987 ◽  
Vol 242 (1) ◽  
pp. 221-226 ◽  
Author(s):  
Y G Assaraf ◽  
L Abu-Elheiga ◽  
D T Spira ◽  
H Desser ◽  
U Bachrach
Keyword(s):  
Amino Acids ◽  
Plasmodium Falciparum ◽  
Dna Synthesis ◽  
Rna Synthesis ◽  
Human Erythrocytes ◽  
Malarial Parasite ◽  
Macromolecular Synthesis ◽  
Irreversible Inhibitor ◽  
Parasite Plasmodium ◽  
Parasite Plasmodium Falciparum

DL-alpha-Difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase, prevented the increases in putrescine and spermidine, but not in spermine, in human erythrocytes infected with the malarial parasite Plasmodium falciparum. The addition of putrescine to these polyamine-depleted cultures restored the normal concentrations of spermidine, whereas that of putrescine even exceeded that of the control cultures. DFMO also inhibited the incorporation of radioactive amino acids into the proteins of parasitized erythrocytes. Electrophoresis on polyacrylamide gels revealed that the synthesis of some proteins was completely blocked by DFMO, but the synthesis of others was not affected. DFMO also caused a partial inhibition of RNA synthesis, and DNA synthesis was completely blocked in polyamine-depleted parasitized erythrocytes. It has been suggested that putrescine and/or spermidine are required for the synthesis of certain proteins in parasitized erythrocytes and that at least one of those proteins is related to the synthesis of DNA of the malarial parasite. It appears that polyamines regulate the schizogony process of P. falciparum.

scholarly journals Polyamine levels and the activity of their biosynthetic enzymes in human erythrocytes infected with the malarial parasite, Plasmodium falciparum

1984 ◽  
Vol 222 (3) ◽  
pp. 815-819 ◽  
Author(s):  
Y G Assaraf ◽  
J Golenser ◽  
D T Spira ◽  
U Bachrach
Keyword(s):  
Plasmodium Falciparum ◽  
Human Erythrocytes ◽  
Malarial Parasite ◽  
Biosynthetic Enzymes ◽  
Irreversible Inhibitor ◽  
Trophozoite Stage ◽  
Polyamine Biosynthesis ◽  
Parasite Plasmodium ◽  
Parasite Plasmodium Falciparum ◽  
Polyamine Content

Human erythrocytes contain only trace amounts of polyamines and lack active polyamine biosynthetic enzymes. A remarkable increase in polyamine content, and in the activity of ornithine and S-adenosyl-L-methionine decarboxylases, is noted in synchronous cultures of the malarial parasite, Plasmodium falciparum. Polyamine biosynthesis reached peak values during the early trophozoite stage, whereas nucleic acid and protein synthesis occurred later in mature trophozoites. DL-alpha-Difluoromethylornithine, an irreversible inhibitor of ornithine decarboxylase, did not interfere with merozoite invasion and with ring-form development, but prevented the transformation of trophozoites to schizonts. Concomitantly, the synthesis of proteins and nucleic acids was significantly inhibited. These inhibitory effects could be readily reversed by the diamine putrescine. Macromolecular synthesis and schizogony were normal when 5-10 mM-DL-alpha-difluoromethylornithine and 0.1 mM-putrescine were added to the cultures simultaneously.

scholarly journals Molecular cloning, characterization and localization of PfPK4, an eIF-2α kinase-related enzyme from the malarial parasite Plasmodium falciparum

1997 ◽  
Vol 328 (2) ◽  
pp. 677-687 ◽  
Author(s):  
Jörg J. MÖHRLE ◽  
Yi ZHAO ◽  
Barbara WERNLI ◽  
M. Richard FRANKLIN ◽  
Barbara KAPPES
Keyword(s):  
Amino Acids ◽  
Plasmodium Falciparum ◽  
Protein Kinase ◽  
Protein Kinases ◽  
Initiation Factor ◽  
Malarial Parasite ◽  
Kinase Gene ◽  
Western Blots ◽  
Parasite Plasmodium ◽  
Parasite Plasmodium Falciparum

PfPK4, a protein kinase gene from the human malarial parasite Plasmodium falciparum, has been cloned utilizing oligonucleotide probing. The gene encodes a protein of a predicted length of 1123 amino acids, and within this amino acid sequence all the conserved regions characteristic of protein kinases can be identified. The catalytic kinase domain possesses highest identities (34-37%) with eukaryotic initiation factor-2α (eIF-2α) kinases, especially haem-regulated inhibitory (HRI) protein kinases. There are two kinase inserts in PfPK4, located at positions common to eIF-2α kinases. The first insert separates kinase subdomains IV and VI by 559 amino acids, and the second subdomains VII and VIII by 41 amino acids. Both inserts are larger than their homologues in eIF-2α kinases. The sequence of PfPK4 has one putative haemin-binding site. The recombinant protein, expressed in Escherichia coli, phosphorylates a synthetic peptide representing a substrate of eIF-2α kinases. Autophosphorylation and substrate phosphorylation are inhibited by haemin. Thus PfPK4 appears to be the first protozoan protein kinase related to eIF-2α kinases and might be the first non-mammalian HRI kinase. Western blots indicated that the protein is expressed as major forms of 80 and 90 kDa. Whereas the 80 kDa form is present throughout the intraerythrocytic development and in merozoites, the two 90 kDa forms are only found in mature parasites. One of the latter is also present in the membrane fraction of erythrocytes harbouring segmenters. Confocal microscopy detected the protein distributed throughout the trophozoite, whereas it was found in discrete foci (punctate distribution) in segmenters. PfPK4 co-localizes with P. falciparum 83 kDa antigen/apical membrane antigen-1 at the apical complex in segmenters and merozoites, but does not co-localize with rhoptry-associated protein-1.

scholarly journals The effect of purified aminoaldehydes produced by polyamine oxidation on the development in vitro of Plasmodium falciparum in normal and glucose-6-phosphate-dehydrogenase-deficient erythrocytes

1986 ◽  
Vol 236 (1) ◽  
pp. 97-101 ◽  
Author(s):  
D M L Morgan ◽  
U Bachrach ◽  
Y G Assaraf ◽  
E Harari ◽  
J Golenser
Keyword(s):  
Plasmodium Falciparum ◽  
Lethal Effect ◽  
Human Erythrocytes ◽  
Malarial Parasite ◽  
Parasite Plasmodium ◽  
Parasite Plasmodium Falciparum ◽  
Development In Vitro ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Polyamine Oxidation

Purified aminoaldehydes produced by polyamine oxidation were toxic to the malarial parasite, Plasmodium falciparum, cultured in human erythrocytes. There was a profound effect on young ring forms, and, during maturation, parasites became more sensitive to the aldehydes. Oxidation of the aldehydes abolished the lethal effect. The plasmodia within glucose-6-phosphate-dehydrogenase (G6PD)-deficient erythrocytes were more sensitive to mono- and di-aldehydes than were parasites in normal erythrocytes. G6PD-deficient erythrocytes were also more sensitive to pretreatment with the dialdehyde produced by the oxidation of spermine. Pretreatment prevented further invasion by the parasites.

scholarly journals Localization of ferrochelatase in Plasmodium falciparum

2004 ◽  
Vol 384 (2) ◽  
pp. 429-436 ◽  
Author(s):  
Sundaramurthy VARADHARAJAN ◽  
B. K. Chandrashekar SAGAR ◽  
Pundi N. RANGARAJAN ◽  
Govindarajan PADMANABAN
Keyword(s):  
Plasmodium Falciparum ◽  
De Novo ◽  
Enzymic Activity ◽  
Malarial Parasite ◽  
Parasite Genome ◽  
Marker Proteins ◽  
Parasite Plasmodium ◽  
Theoretical Predictions ◽  
Parasite Plasmodium Falciparum

Our previous studies have demonstrated de novo haem biosynthesis in the malarial parasite (Plasmodium falciparum and P. berghei). It has also been shown that the first enzyme of the pathway is the parasite genome-coded ALA (δ-aminolaevulinate) synthase localized in the parasite mitochondrion, whereas the second enzyme, ALAD (ALA dehydratase), is accounted for by two species: one species imported from the host red blood cell into the parasite cytosol and another parasite genome-coded species in the apicoplast. In the present study, specific antibodies have been raised to PfFC (parasite genome-coded ferrochelatase), the terminal enzyme of the haem-biosynthetic pathway, using recombinant truncated protein. With the use of these antibodies as well as those against the hFC (host red cell ferrochelatase) and other marker proteins, immunofluorescence studies were performed. The results reveal that P. falciparum in culture manifests a broad distribution of hFC and a localized distribution of PfFC in the parasite. However, PfFC is not localized to the parasite mitochondrion. Immunoelectron-microscopy studies reveal that PfFC is indeed localized to the apicoplast, whereas hFC is distributed in the parasite cytoplasm. These results on the localization of PfFC are unexpected and are at variance with theoretical predictions based on leader sequence analysis. Biochemical studies using the parasite cytosolic and organellar fractions reveal that the cytosol containing hFC accounts for 80% of FC enzymic activity, whereas the organellar fraction containing PfFC accounts for the remaining 20%. Interestingly, both the isolated cytosolic and organellar fractions are capable of independent haem synthesis in vitro from [4-14C]ALA, with the cytosol being three times more efficient compared with the organellar fraction. With [2-14C]glycine, most of the haem is synthesized in the organellar fraction. Thus haem is synthesized in two independent compartments: in the cytosol, using the imported host enzymes, and in the organellar fractions, using the parasite genome-coded enzymes.

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