Marine picocyanobacterial PhnD1 shows specificity for various phosphorus sources but likely represents a constitutive inorganic phosphate transporter.

Despite being fundamental to multiple biological processes, phosphorus (P) availability in marine environments is often growth-limiting, with generally low surface concentrations. Picocyanobacteria strains encode a putative ABC-type phosphite/phosphate/phosphonate transporter, phnDCE, thought to provide access to an alternative phosphorus pool. This, however, is paradoxical given most picocyanobacterial strains lack known phosphite degradation or carbon-phosphate lyase pathway to utilise alternate phosphorus pools. To understand the function of the PhnDCE transport system and its ecological consequences, we characterised the PhnD1 binding proteins from four distinct marine Synechococcus isolates (CC9311, CC9605, MITS9220, and WH8102). We show the Synechococcus PhnD1 proteins selectively bind phosphorus compounds with a stronger affinity for phosphite than for phosphate or methyl phosphonate. However, based on our comprehensive ligand screening and growth experiments showing Synechococcus strains WH8102 and MITS9220 cannot utilise phosphite or methylphosphonate as a sole phosphorus source, we hypothesise that the picocyanobacterial PhnDCE transporter is a constitutively expressed, medium-affinity phosphate transporter, and the measured affinity of PhnD1 to phosphite or methyl phosphonate is fortuitous. Our MITS9220_PhnD1 structure explains the comparatively lower affinity of picocyanobacterial PhnD1 for phosphate, resulting from a more limited H-bond network. We propose two possible physiological roles for PhnD1. First, it could function in phospholipid recycling, working together with the predicted phospholipase, TesA, and alkaline phosphatase. Second, by having multiple transporters for P (PhnDCE and Pst), picocyanobacteria could balance the need for rapid transport during transient episodes of higher P availability in the environment, with the need for efficient P utilisation in typical phosphate-deplete conditions.

Crystallographic approach to fragment-based hit discovery against Schistosoma mansoni purine nucleoside phosphorylase.

Several Schistosoma species cause Schistosomiasis, an endemic disease in 78 countries that is ranked second amongst the parasitic diseases in terms of its socioeconomic impact and human health importance. The drug recommended for treatment by the WHO is praziquantel (PZQ), but there are concerns associated with PZQ, such as the lack of information about its exact mechanism of action, its high price, its effectiveness - which is limited to the parasite's adult form - and reports of resistance. The parasites lack the de novo purine pathway, rendering them dependent on the purine salvage pathway or host purine bases for nucleotide synthesis. Thus, the Schistosoma purine salvage pathway is an attractive target for the development of necessary and selective new drugs. In this study, the purine nucleotide phosphorylase II (PNP2), a new isoform of PNP1, was submitted to a high-throughput fragment-based hit discovery using a crystallographic screening strategy. PNP2 was crystallized and crystals were soaked with 827 fragments, a subset of the Maybridge 1000 library. X-ray diffraction data was collected and structures were solved. Out of 827-screened fragments we have obtained a total of 19 fragments that show binding to PNP2. Fourteen of these fragments bind to the active site of PNP2, while five were observed in three other sites. Here we present the first fragment screening against PNP2.

Substituted 2-(2-aminopyrimidin-4-yl)pyridine-4-carboxylates as potent inhibitors of JumonjiC domain-containing histone demethylases.

BACKGROUND: Aberrant expression of iron(II)- and 2-oxoglutarate-dependent JumonjiC histone demethylases has been linked to cancer. Potent demethylase inhibitors are drug candidates and biochemical tools to elucidate the functional impact of demethylase inhibition. METHODS & RESULTS: Virtual screening identified a novel lead scaffold against JMJD2A with low-micromolar potency in vitro. Analogs were acquired from commercial sources respectively synthesized in feedback with biological testing. Optimized compounds were transformed into cell-permeable prodrugs. A cocrystal x-ray structure revealed the mode of binding of these compounds as competitive to 2-oxoglutarate and confirmed kinetic experiments. Selectivity studies revealed a preference for JMJD2A and JARID1A over JMJD3. CONCLUSION: Virtual screening and rational structural optimization led to a novel scaffold for highly potent and selective JMJD2A inhibitors.