David J Johnson

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Chloroquine resistance (CQR) in Plasmodium falciparum is associated with mutations in the digestive vacuole transmembrane protein PfCRT. However, the contribution of individual pfcrt mutations has not been clarified and other genes have been postulated to play a substantial role. Using allelic exchange, we show that removal of the single PfCRT amino-acid(More)
Tetrahydrofolates are essential cofactors for DNA synthesis and methionine metabolism. Malaria parasites are capable both of synthesizing tetrahydrofolates and precursors de novo and of salvaging them from the environment. The biosynthetic route has been studied in some detail over decades, whereas the molecular mechanisms that underpin the salvage pathway(More)
BACKGROUND Plasmodium falciparum chloroquine resistance (CQR) transporter protein (PfCRT) is known to be the important key of CQR. Recent studies have definitively demonstrated a link between mutations in the gene pfcrt and resistance to chloroquine in P. falciparum. Although these mutations are predictive of chloroquine resistance, they are not(More)
Acquired resistance to therapeutic agents is a major clinical concern in the prevention/treatment of malaria. The parasite has developed resistance to specific drugs through two mechanisms: mutations in target proteins such as dihydrofolate reductase and the bc1 complex for antifolates and nathoquinones, respectively, and alterations in predicted parasite(More)
Cathepsin G (CatG), a serine protease found in the azurophil granules of neutrophils, participates in killing engulfed microorganisms. CatG is a poorly understood enzyme, in part because it can only be obtained as mature enzyme purified from human blood, and because it seems to have dual specificity for chymotrypsin-like and trypsin-like substrates.(More)
Human neutrophils are the most abundant type of white blood cell and provide the body with a line of defense against foreign, infectious microorganisms. Contained within the azurophilic granules in the cytoplasm of neutrophils are three serine proteases, Human Neutrophil Elastase, Cathepsin G, and Protease 3. Once a foreign bacterium is engulfed by white(More)
This paper will discuss the use and security of shared accounts. While shared accounts exist on other systems, this paper has been limited in scope to focus on UNIX-and Microsoft Windows-based systems, however the basic principles should be applicable to other systems as well. The paper will start by defining what shared accounts are, some of their uses,(More)
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