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Biomedical subjects

I A Hope

Publications and source records attributed to I A Hope.

24 records · Page 2Linked to original sources
PubMed1985

GCN4 protein, synthesized in vitro, binds HIS3 regulatory sequences: implications for general control of amino acid biosynthetic genes in yeast.

The yeast GCN4 gene product is necessary for the transcriptional induction of many amino acid biosynthetic genes in response to conditions of amino acid starvation. We synthesized radioactively pure GCN4 protein by in vitro translation of mRNA produced by in vitro transcription with SP6 RNA polymerase. GCN4 protein binds specifically to the 20 bp region of the HIS3 gene that is critical for transcriptional regulation in vivo and contains the TGACTC sequence common to coregulated genes. A synthetic GCN4 mutant protein lacking the 40 C-terminal amino acids fails to bind DNA; this correlates with a gcn4 mutant gene that is nonfunctional in vivo. Finally, GCN4 protein binds to the promoter regions of coordinately regulated genes, but not to analogous regions of other genes. We suggest that GCN4 protein is a specific transcription factor, and we describe a molecular model for the general control of amino acid biosynthetic genes.

Base Sequence↗
PubMed1984

Characterisation and translation studies of messenger RNA from the human malaria parasite Plasmodium falciparum and construction of a cDNA library.

RNA was isolated from trophozoites, schizonts and mixed populations of Plasmodium falciparum. 5% of the total was poly(A+) message, of average length 1.2 kb (10-12 kb maximum) and a poly(A) content of 10%. The mRNA fractions could be translated in vitro by reticulocyte lysates supplemented either with exogenous or P. falciparum tRNA. The patterns from two independent isolates, one cloned (T9-94) and one uncloned (K1) were virtually identical. Major translation products from 16-230 kDa have been measured. The most abundant is lactate dehydrogenase (34.8 kDa). Trophozoite mRNA codes principally for proteins of less than or equal to 93 kDa, while schizont mRNA codes for additional proteins of higher molecular mass. There are marked similarities between the in vitro translation products and proteins synthesised in vivo in synchronous cultures. A number of schizont mRNA translation products (principally those of 230, 203, 185, 170, 115, 101 and 71 kDa) are specifically precipitated without post-translational modification by sera from humans exposed to malaria. A cDNA library has been constructed in phage lambda from total poly(A+) RNA and partially characterised. About 10% of the clones derive from abundant mRNA sequences. Putative actin clones have been isolated from this library and the parasite actin mRNA sized at approx. 2.8 kb.

Actins↗
PubMed1984

Processing, polymorphism, and biological significance of P190, a major surface antigen of the erythrocytic forms of Plasmodium falciparum.

A detailed analysis of P190, a major surface associated protein of Plasmodium falciparum erythrocytic stages has been undertaken. We have demonstrated that this protein is recognised by two monoclonal antibodies, one of which recognises a constant feature (2.2) and one a variable feature (7.3). Cell free protein synthesis demonstrates that the variable 7.3 epitope is encoded in the structural gene for P190. The 7.3 epitope is only present on late trophozoites and schizonts whilst the 2.2 epitope is present on all erythrocytic stages. Labelling of synchronised cultures demonstrates that P190 is made only from 30 h onwards, (i.e. by trophozoites and schizonts). By pulse chase analysis we show that P190 undergoes processing and is lost at release/re-invasion, correlating with a lack of 7.3 immunofluorescence reactivity on rings. Sera from Nigeria recognise P190 from a Thai isolate of malaria. They also react with purified P190 in a micro-ELISA assay. A model for the role of P190 in re-invasion is presented, and the possible clinical significance of this protein is discussed.

Animals↗
PubMedDate not supplied

Evidence for immunological cross-reaction between sporozoites and blood stages of a human malaria parasite.

Malaria parasites (Plasmodium spp.) show a complex pattern of development in the mammalian host and many studies support the view that the surface of the sporozoite, injected by the mosquito, has no antigens in common with the erythrocytic stage of development. For example, immunization with the erythrocytic parasites generates antisera with negligible titre by indirect immunofluorescence to the sporozoite surface. Although monoclonal antibodies prepared against erythrocytic stages were reported to show cross-reaction to the sporozoite stage, this appeared to be due to cytoplasmic antigens exposed by the method of sporozoite preparation, and in Plasmodium knowlesi, a cDNA clone coding for the circumsporozoite antigen, the major protein of the sporozoite surface, showed no hydridization to mRNA isolated from the erythrocytic stages. Here, however, we present evidence for an antigenic determinant shared by the sporozoite surface and the erythrocytic stages of the human malaria parasite, P. falciparum. Moreover, our studies show that the antigen(s) elicit a strong immune response in man.

Animals↗
PubMedDate not supplied

Major surface antigen gene of a human malaria parasite cloned and expressed in bacteria.

The late blood stages of the human malaria parasite, Plasmodium falciparum, carry a major surface antigen, p190, of molecular weight (Mr) 190,000. This antigenically variable protein is actively processed, first as the parasite matures and again when it is released into the blood stream and invades a new erythrocyte to initiate a cycle of growth. It elicits a strong immune response in man; all tested adult sera from endemic areas have antibodies against this protein. Our evidence indicates that purified p190 can alter the course of parasitaemia in monkeys with falciparum malaria. We have also succeeded in cloning part of the gene for p190 and expressing it in Escherichia coli. To this end we have developed a new technique, antibody select, which greatly simplifies final identification of expressing clones.

Animals↗