Wild-Type Phosphoribosylpyrophosphate Synthase (PRS) from Mycobacterium tuberculosis: A Bacterial Class II PRS?

The 5-phospho-α-D-ribose 1-diphosphate (PRPP) metabolite plays essential roles in several biosynthetic pathways, including histidine, tryptophan, nucleotides, and, in mycobacteria, cell wall precursors. PRPP is synthesized from α-D-ribose 5-phosphate (R5P) and ATP by the Mycobacterium tuberculosis prsA gene product, phosphoribosylpyrophosphate synthase (MtPRS). Here, we report amplification, cloning, expression and purification of wild-type MtPRS. Glutaraldehyde cross-linking results suggest that MtPRS predominates as a hexamer, presenting varied oligomeric states due to distinct ligand binding. MtPRS activity measurements were carried out by a novel coupled continuous spectrophotometric assay. MtPRS enzyme activity could be detected in the absence of Pi. ADP, GDP and UMP inhibit MtPRS activity. Steady-state kinetics results indicate that MtPRS has broad substrate specificity, being able to accept ATP, GTP, CTP, and UTP as diphosphoryl group donors. Fluorescence spectroscopy data suggest that the enzyme mechanism for purine diphosphoryl donors follows a random order of substrate addition, and for pyrimidine diphosphoryl donors follows an ordered mechanism of substrate addition in which R5P binds first to free enzyme. An ordered mechanism for product dissociation is followed by MtPRS, in which PRPP is the first product to be released followed by the nucleoside monophosphate products to yield free enzyme for the next round of catalysis. The broad specificity for diphosphoryl group donors and detection of enzyme activity in the absence of Pi would suggest that MtPRS belongs to Class II PRS proteins. On the other hand, the hexameric quaternary structure and allosteric ADP inhibition would place MtPRS in Class I PRSs. Further data are needed to classify MtPRS as belonging to a particular family of PRS proteins. The data here presented should help augment our understanding of MtPRS mode of action. Current efforts are toward experimental structure determination of MtPRS to provide a solid foundation for the rational design of specific inhibitors of this enzyme

Multiple paternity in leopard shark (Triakis semifasciata) litters sampled from a predominantly female aggregation in La Jolla, California, USA

The number of sires per litter was determined for the leopard shark (Triakidae: Triakis semifasciata) to investigate the potential effect of female-biased aggregation behavior on the frequency of multiple paternity (FMP). Four highly polymorphic microsatellite markers were developed and used to genotype 449 pups from 22 litters (20.4±7.0 pups per litter) sampled from pregnant females collected from a female-dominated leopard shark aggregation in La Jolla, California, USA. Multiple paternity was detected in 8 of 22 litters (FMP=36.4%), each having two sires per litter. The relatively low FMP (compared to other shark species) is generally consistent with the hypothesis that female aggregation behavior reduces mating attempts by males and thus limits genetic polyandry. Significant interannual variability in FMP observed between two years of the study (2010: FMP=20.0%, n=10, and 2011: FMP=83.3%, n=6) appears to be correlated with the frequency of males in the aggregation. Although females may benefit indirectly from mating with multiple males by promoting sperm competition and hedging against nonviable sperm, the most probable explanation for genetic polyandry in the leopard shark appears to be "convenience polyandry," where females acquiesce to superfluous mating attempts if the costs of resistance outweigh the costs of capitulation. Thus, FMP is expected to increase as the male-to-female ratio increases and as capacity of females to resist coercive males decreases at the time and place of mating. © 2013 Elsevier B.V

Multiple paternity in leopard shark (Triakis semifasciata) litters sampled from a predominantly female aggregation in La Jolla, California, USA

The number of sires per litter was determined for the leopard shark (Triakidae: Triakis semifasciata) to investigate the potential effect of female-biased aggregation behavior on the frequency of multiple paternity (FMP). Four highly polymorphic microsatellite markers were developed and used to genotype 449 pups from 22 litters (20.4±7.0 pups per litter) sampled from pregnant females collected from a female-dominated leopard shark aggregation in La Jolla, California, USA. Multiple paternity was detected in 8 of 22 litters (FMP=36.4%), each having two sires per litter. The relatively low FMP (compared to other shark species) is generally consistent with the hypothesis that female aggregation behavior reduces mating attempts by males and thus limits genetic polyandry. Significant interannual variability in FMP observed between two years of the study (2010: FMP=20.0%, n=10, and 2011: FMP=83.3%, n=6) appears to be correlated with the frequency of males in the aggregation. Although females may benefit indirectly from mating with multiple males by promoting sperm competition and hedging against nonviable sperm, the most probable explanation for genetic polyandry in the leopard shark appears to be "convenience polyandry," where females acquiesce to superfluous mating attempts if the costs of resistance outweigh the costs of capitulation. Thus, FMP is expected to increase as the male-to-female ratio increases and as capacity of females to resist coercive males decreases at the time and place of mating. © 2013 Elsevier B.V

Considering connections between Hollywood and biodiversity conservation

Cinema offers a substantial opportunity to share messages with a wide audience. Given its global range and potentially high impact, there is an urgent need for research that evaluates the effects of this form of visual media on conservation outcomes. Cinema can influence the awareness and behaviours of non-specialist audiences, and could therefore play an important positive and/or negative role in biodiversity conservation through behavioural change and social pressure on key stakeholders and policy makers. Limited awareness about the potential benefits and limitations of cinema for conservation, as well as a lack of evidence about impacts, currently hinder our ability to learn from previous and ongoing initiatives, and to engage productively with the movie industry. We discuss the key opportunities and risks that arise from cinematic representations of conservation issues and species of concern, making use of examples and case studies where they are available. We additionally provide a framework that enables conservationists to better understand and engage with the film industry, highlighting how this can facilitate engagement with the movie industry, harness its potential, and improve work to mitigate any negative consequences. A robust evidence base is key for evaluating and planning these engagements, and for informing related policy and management decisions