The primary structure of histone H2B from the mollusc Patella granatina

Histones H2B were isolated from the gonads of a mollusc (Patella granatina) and from chicken (Gallus domesticus), crocodile (Crocodylus niloticus) and amphibian (Xenopus laevis) erythrocytes. The H2B's were purified by ion-exchange and gel exclusion chromatography. The complete primary structure of the mollusc hi stone H2B t 11 has been deduced from the sequences established of pa e a adjoining and overlapping peptides by the Edman degradation procedure. The partial structure of H2B from chicken erythrocytes (87 residues), crocodile erythrocytes (75 residues) and Xenopus erythrocytes (63 residues) was also established. The amino acid sequences are compared to those of other histones H2B. The effect of mutations on the predicted secondary structure of histone H2B is considered

Toxoplasmosis In South Africa- Old Disease In A New Context

Toxoplasmosis is one of the most widespread parasitic infections known. Clinical manifestation of toxoplasmosis because of immunosuppression is typically due to a reactivation of a chronic infection.  According to the UNAIDS 2008 report on the global AIDS epidemic, about 5.7 million South Africans were infected and living with HIV in 2007, with obvious risk and health resource implications for toxoplasmosis. T. gondii has been largely neglected as a health risk to the general population in the HIV era. Currently South Africa is burdened with ongoing HIV and TB pandemics. South Africa accounts for 17% of the global HIV burden and has a TB incidence of 950 per 100,000 as at 2012. Such high incidence of immunosuppressive infections puts the population at a high risk of opportunistic infections such as toxoplasmosis. Seroprevalence rates in Africa are high in both human and animal populations, but there are no reports on the significance of the pathogen within the food or water chain of African cultures. Future work should focus on a more systematic approach towards Toxoplasma gondii seroprevalence data gathering and analysis in order to inform on effective approaches to its prevention and disease reduction, and on the molecular epidemiology of the pathogen within the South African context. Keywords: Toxoplasma gondii, behavior, toxoplasmosis, mental health, sero-prevalence, South Africa, disease burden, HEU, HUU

Glutamine synthetase sequence evolution in the mycobacteria and their use as molecular markers for Actinobacteria speciation

<p>Abstract</p> <p>Background</p> <p>Although the gene encoding for glutamine synthetase (<it>gln</it>A) is essential in several organisms, multiple glnA copies have been identified in bacterial genomes such as those of the phylum <it>Actinobacteria</it>, notably the mycobacterial species. Intriguingly, previous reports have shown that only one copy (<it>gln</it>A1) is essential for growth in <it>M. tuberculosis</it>, while the other copies (<it>gln</it>A2, <it>gln</it>A3 and <it>gln</it>A4) are not.</p> <p>Results</p> <p>In this report it is shown that the <it>gln</it>A1 and <it>gln</it>A2 encoded glutamine synthetase sequences were inherited from an <it>Actinobacteria </it>ancestor, while the <it>gln</it>A4 and <it>gln</it>A3 encoded GS sequences were sequentially acquired during <it>Actinobacteria </it>speciation. The glutamine synthetase sequences encoded by <it>gln</it>A4 and <it>gln</it>A3 are undergoing reductive evolution in the mycobacteria, whilst those encoded by <it>gln</it>A1 and <it>gln</it>A2 are more conserved.</p> <p>Conclusion</p> <p>Different selective pressures by the ecological niche that the organisms occupy may influence the sequence evolution of <it>gln</it>A1 and <it>gln</it>A2 and thereby affecting phylogenies based on the protein sequences they encode. The findings in this report may impact the use of similar sequences as molecular markers, as well as shed some light on the evolution of glutamine synthetase in the mycobacteria.</p

Glutamate dehydrogenase and glutamine synthetase are regulated in response to nitrogen availability in Myocbacterium smegmatis

<p>Abstract</p> <p>Background</p> <p>The assimilation of nitrogen is an essential process in all prokaryotes, yet a relatively limited amount of information is available on nitrogen metabolism in the mycobacteria. The physiological role and pathogenic properties of glutamine synthetase (GS) have been extensively investigated in <it>Mycobacterium tuberculosis</it>. However, little is known about this enzyme in other mycobacterial species, or the role of an additional nitrogen assimilatory pathway via glutamate dehydrogenase (GDH), in the mycobacteria as a whole. We investigated specific enzyme activity and transcription of GS and as well as both possible isoforms of GDH (NAD⁺- and NADP⁺-specific GDH) under varying conditions of nitrogen availability in <it>Mycobacterium smegmatis </it>as a model for the mycobacteria.</p> <p>Results</p> <p>It was found that the specific activity of the aminating NADP⁺-GDH reaction and the deaminating NAD⁺-GDH reaction did not change appreciably in response to nitrogen availability. However, GS activity as well as the deaminating NADP⁺-GDH and aminating NAD⁺-GDH reactions were indeed significantly altered in response to exogenous nitrogen concentrations. Transcription of genes encoding for GS and the GDH isoforms were also found to be regulated under our experimental conditions.</p> <p>Conclusions</p> <p>The physiological role and regulation of GS in <it>M. smegmatis </it>was similar to that which has been described for other mycobacteria, however, in our study the regulation of both NADP⁺- and NAD⁺-GDH specific activity in <it>M. smegmatis </it>appeared to be different to that of other Actinomycetales. It was found that NAD⁺-GDH played an important role in nitrogen assimilation rather than glutamate catabolism as was previously thought, and is it's activity appeared to be regulated in response to nitrogen availability. Transcription of the genes encoding for NAD⁺-GDH enzymes seem to be regulated in <it>M. smegmatis </it>under the conditions tested and may contribute to the changes in enzyme activity observed, however, our results indicate that an additional regulatory mechanism may be involved. NADP⁺-GDH seemed to be involved in nitrogen assimilation due to a constitutive aminating activity. The deaminating reaction, however was observed to change in response to varying ammonium concentrations which suggests that NADP⁺-GDH is also regulated in response to nitrogen availability. The regulation of NADP⁺-GDH activity was not reflected at the level of gene transcription thereby implicating post-transcriptional modification as a regulatory mechanism in response to nitrogen availability.</p