Biomedical subjects

J Scaife

Publications and source records attributed to J Scaife.

At least 19 recordsLinked to original sources

PubMed1991

The complete sequence of a Plasmodium malariae SSUrRNA gene and its comparison to other plasmodial SSUrRNA genes.

A gene encoding the small subunit rRNA (SSUrRNA) has been isolated from the human parasite, Plasmodium malariae. The gene has been sequenced. It contains conserved and variable regions which conform to patterns established for other eukaryotic SSUrRNA genes. Comparisons with other SSUrRNA genes from Plasmodium species reveal regions unique to P. malariae which could be used in specific diagnostic probes for this organism, and provide evidence that the gene is of the type expressed during asexual growth. In addition the '5.8S' gene has been cloned from P. malariae. The gene has been sequenced. It contains bases universally conserved in '5.8S' genes but there is considerable divergence between the P. malariae sequence and that of the P. falciparum gene.

Animals↗

PubMed1990

The gene for hypoxanthine phosphoribosyl transferase of Plasmodium falciparum complements a bacterial HPT mutation.

The enzyme hypoxanthine phosphoribosyl transferase of Plasmodium falciparum has been overexpressed in Escherichia coli. The protein was found to be active enzymatically. When the recombinant expression vector (pPfPRT2) was transformed and expressed in a Salmonella typhimurium mutant KP1684 (purE deoD hpt gpt), the active expressed protein complemented the hpt mutation in the bacteria. We discuss the practical value of this strain. Assays of the expressed protein in the mutant extract showed that the enzyme is able to use hypoxanthine, guanine and xanthine as substrates. A specificity study using the competitive inhibitor, 6-thioguanine, showed that of these hypoxanthine is the most favourable substrate. The biological significance of xanthine utilisation by the enzyme is discussed.

Animals↗

PubMed1988

Epitopes recognized by human T cells map within the conserved part of the GP190 of P. falciparum.

In a study aimed at developing a vaccine against the asexual blood stages of Plasmodium falciparum, two T cell epitopes were identified within a nonpolymorphic region of gp190 of Plasmodium falciparum merozoites. The two epitopes, which were revealed by deletion analysis, stimulated human T cell clones. Peptides containing sequences of the epitopes stimulated the cloned T cells and peripheral blood mononuclear cells (PBMC) from malaria-infected individuals. Moreover, the T cell clones responded to 11 different Plasmodium falciparum isolates in culture, showing that the epitopes are recognized in native parasites.

Amino Acid Sequence↗

PubMed1987

A malaria protein exported into a new compartment within the host erythrocyte.

A Plasmodium falciparum protein which is exported into a new compartment in the host erythrocyte has been located. This protein, exp-1, has a variable region recognized by a monoclonal antibody. Naturally occurring mutants of this region have been characterized. All mutants studied so far have the same A----G transition abolishing the target for the antibody. The exp-1 gene has a complex structure containing two introns. It is highly conserved in five independent, genetically defined parasite lines, suggesting that exp-1 has an important function. We discuss the possible role of exp-1 in P. falciparum infections.

Amino Acid Sequence↗

PubMed1986

Characterisation of a repetitive DNA sequence from the malaria parasite, Plasmodium falciparum.

A repetitive DNA fragment cloned from the malaria parasite, Plasmodium falciparum, has been analysed. It contains a 21 base pair sequence which occurs in multiple tandem repeats. Two clusters of the same repeat are found in opposite orientations on the same DNA fragment. The repetitive DNA provides an additional way to distinguish between different strains of parasite by hybridisation to genomic blots and may serve as a species-specific probe for diagnosis.

Animals↗

PubMed1986

In vivo time course of synthesis and processing of major schizont membrane polypeptides in Plasmodium falciparum.

A rapid method of separating membrane co-sedimentable and soluble components of Plasmodium infected erythrocytes is presented. We propose a nomenclature for major P. falciparum polypeptides, applicable to different isolates and based on their cellular location and stage specificity. For four of these polypeptides (185 kDa = Mp1; 120 kDa = Mp3; 76 kDa = Mp5; 90 kDa= Sp2) supposed to play a role in protective immunity, monospecific antibodies were available. We have studied their fate at the time of merozoïte release and reinvasion, and the possible correlations between these polypeptides, by pulse-chase experiments.

Animals↗

PubMed1986

Antigens of Plasmodium falciparum blood stages with clinical interest cloned and expressed in E. coli.

Explore the source record for details and available documents.

Animals↗

PubMed1985

Polymorphism of the precursor for the major surface antigens of Plasmodium falciparum merozoites: studies at the genetic level.

The gene for the precursor of Plasmodium falciparum merozoite surface antigens has been cloned. The entire sequence of the gene from a Thai isolate of the parasite is reported. It provides evidence for a signal peptide, a region containing short repeating peptides and an anchor sequence. In addition, the 5' end of a Papua New Guinea isolate has been sequenced. Comparison of these and other sequences defines, at the genetic level, a polymorphic region in the protein, and suggests that other parts of the protein are less susceptible to variation. Furthermore it appears that several signal peptides of P. falciparum exhibit extensive sequence homologies.

Amino Acid Sequence↗

PubMed1985

The gene for an exported antigen of the malaria parasite Plasmodium falciparum cloned and expressed in Escherichia coli.

An exported protein of the erythrocytic stages of the malaria parasite, Plasmodium falciparum, has epitope(s) in common with the surface of the sporozoite stage (1). Two cDNA clones encoding this protein, Ag5.1, have now been isolated and expressed in Escherichia coli. The coding sequence contains a region with strong homology to that of the circumsporozoite protein of P. falciparum. Other features of the sequence can be explained in terms of the observed behaviour of the protein in the parasite life cycle. The Ag5.1 can now be synthesised in bacteria in sufficient amounts to analyse the immune response to this protein.

Amino Acid Sequence↗

PubMed1985

Cloning studies on the gene coding for L-(+)-lactate dehydrogenase of Plasmodium falciparum.

We show that the L-(+)-lactate dehydrogenase (EC 1.1.1.27;L-lactate: NAD+-oxidoreductase) of Plasmodium falciparum (LDH-P) is encoded in the parasite genome. A monoclonal antibody (McAb 7.2) has been shown to bind the LDH-P subunit which has an apparent molecular mass of 35 kDa. A polyclonal antiserum raised against affinity purified LDH-P has been used to isolate cDNA clones containing LDH-P epitopes from a lambda gt11Tn5 expression library. DNA sequence analysis of one clone, lambda LDH-P.1, reveals a single open reading frame which shows a degree of homology to the N-terminal domain of known LDH amino acid sequences.

Amino Acid Sequence↗

PubMed1983

Antigens of the erythrocytes stages of the human malaria parasite Plasmodium falciparum detected by monoclonal antibodies.

A range of 22 mouse anti-P. falciparum monoclonal antibodies have been characterized by indirect immunofluorescence and immunoprecipitation. On the basis of these studies, 5 groups of antibodies and 6 classes of antigen were defined. Group I antibodies give, bright, uniform, generalised staining of all blood stages including gametocytes. Three of these antibodies precipitate a metabolically labelled molecule(s) of 35 kDa. One precipitates a 50 kDa antigen. Group II antibodies, which give strong localised immunofluorescence in merozoites, and a weak diffuse pattern in earlier stages, precipitate biosynthetically labelled molecules of 160 kDa. Group III antibodies react with all asexual stages. With merozoites they produce intense staining around the perimeter, both in fixed and unfixed preparations. They precipitate biosynthetic molecules of 190 kDa. Group IV antibodies are identical to Group III except they are stage restricted to schizonts and merozoites. They also precipitate 190 kDa antigens. These, however, in contrast to group III, are readily accessible to 125I-lactoperoxidase labelling. One antibody also precipitates a set of smaller peptides. Finally, Group V antibodies produce very bright ill-defined staining of pigment-containing parasites, as well as of inclusions in the red cell. They precipitate a series of molecules of 160, 60 and 35 kDa which are readily accessible to 125I. The 160 kDa molecule is also labelled by [35S]methionine. These results are discussed in the context of the development of a malaria vaccine and immunodiagnostic tests.

Animals↗

PubMed1979

Lambda transducing bacteriophage carrying deletions of the argCBH-rpoBC region of the Escherichia coli chromosome.

Deletions in the rpoBC region have been transferred to phage lambda and characterized in detail by genetic, structural, and functional tests. We thus extend and confirm knowledge of the organization of this part of the chromosome. The new phages are useful tools for studying the genes for the bacterial transcription and translation machinery.

Bacteriophage lambda↗

PubMed1978

Identification of a single promoter in E. coli for rplJ, rplL and rpoBC.

A set of restriction fragments cloned into phage lambda vectors has allowed us to locate a site necessary for full rpoBC expression. We find that these genes for the two large subunits of RNA polymerase and the genes, rplL and rplJ, for two ribosomal proteins, form a single operon.

Bacterial Proteins↗

PubMed1975

Induction of RNA polymerase synthesis in Escherichia coli.

Studies on the rate of synthesis of the beta and beta' subunits of RNA polymerase in haploid strains of Escherichia coli K12 containing poorly-suppressed rif degrees am mutations provide conclusive evidence that synthesis of at least these two subunits is regulated.

DNA-Directed RNA Polymerases↗

PubMed1974