We present a net-shaped DNA nanostructure (called “DNA Net” herein) design strategy for selective recognition and high-affinity capture of intact SARS-CoV-2 virions through spatial pattern-matching and multivalent interactions between the aptamers (targeting wild-type spike-RBD) positioned on the DNA Net and the trimeric spike glycoproteins displayed on the viral outer surface. Carrying a designer nanoswitch, the DNA Net-aptamers release fluorescence signals upon virus binding that are easily read with a handheld fluorimeter for a rapid (in 10 min), simple (mix-and-read), sensitive (PCR equivalent), room temperature compatible, and inexpensive (∼$1.26/test) COVID-19 test assay. The DNA Net-aptamers also impede authentic wild-type SARS-CoV-2 infection in cell culture with a near 1 × 10 3 -fold enhancement of the monomeric aptamer. Furthermore, our DNA Net design principle and strategy can be customized to tackle other life-threatening and economically influential viruses like influenza and HIV, whose surfaces carry class-I viral envelope glycoproteins like the SARS-CoV-2 spikes in trimeric forms.

The current COVID-19 outbreak warrants the design and development of novel anti-COVID therapeutics. Using a combination of bioinformatics and computational tools, we modelled the 3D structure of the RdRp (RNA-dependent RNA polymerase) of SARS-CoV2 (severe acute respiratory syndrome coronavirus-2) and predicted its probable GTP binding pocket in the active site. GTP is crucial for the formation of the initiation complex during RNA replication. This site was computationally targeted using a number of small molecule inhibitors of the hepatitis C RNA polymerase reported previously. Further optimizations suggested a lead molecule that may prove fruitful in the development of potent inhibitors against the RdRp of SARS-CoV2.

causes tuberculosis in humans and predominantly infects alveolar macrophages. To survive inside host lesions and to evade immune surveillance, this pathogen has developed many strategies. For example, uses host-derived lipids/fatty acids as nutrients for prolonged persistence within hypoxic host microenvironments. imports these metabolites through its respective transporters, and in the case of host fatty acids, a pertinent question arises: does have the enzyme(s) for cleavage of fatty acids from host lipids? We show herein that a previously uncharacterized membrane-associated protein encoded by is conserved exclusively in actinomycetes, exhibits both lipase and protease activities, is secreted into macrophages, and catalyzes host lipid hydrolysis. In light of these functions, we annotated Rv2672 as mycobacterial secreted hydrolase 1 (Msh1). Furthermore, we found that this enzyme is up-regulated both in an model of hypoxic stress and in a mouse model of infection, suggesting that the pathogen requires Msh1 under hypoxic conditions. Silencing Msh1 expression compromised the ability of to proliferate inside lipid-rich foamy macrophages but not under regular culture conditions , underscoring Msh1's importance for persistence in lipid-rich microenvironments. Of note, this is the first report providing insight into the mechanism of host lipid catabolism by an enzyme, augmenting our current understanding of how meets its nutrient requirements under hypoxic conditions.

Intracellular pathogens including Mycobacterium tuberculosis (Mtb) have evolved with strategies to uptake amino acids from host cells to fulfil their metabolic requirements. However, Mtb also possesses de novo biosynthesis pathways for all the amino acids. This raises a pertinent question- how does Mtb meet its histidine requirements within an in vivo infection setting? Here, we present a mechanism in which the host, by up-regulating its histidine catabolizing enzymes through interferon gamma (IFN-γ) mediated signalling, exerts an immune response directed at starving the bacillus of intracellular free histidine. However, the wild-type Mtb evades this host immune response by biosynthesizing histidine de novo, whereas a histidine auxotroph fails to multiply. Notably, in an IFN-γ−/− mouse model, the auxotroph exhibits a similar extent of virulence as that of the wild-type. The results augment the current understanding of host-Mtb interactions and highlight the essentiality of Mtb histidine biosynthesis for its pathogenesis.

The absence of a histidine biosynthesis pathway in humans, coupled with histidine essentiality for survival of the important human pathogen (), underscores the importance of the bacterial enzymes of this pathway as major antituberculosis drug targets. However, the identity of the mycobacterial enzyme that functions as the histidinol phosphate phosphatase (HolPase) of this pathway remains to be established. Here, we demonstrate that the enzyme encoded by the gene, belonging to the inositol monophosphatase (IMPase) family, functions as the HolPase and specifically dephosphorylates histidinol phosphate. The crystal structure of Rv3137 in apo form enabled us to dissect its distinct structural features. Furthermore, the holo-complex structure revealed that a unique cocatalytic multizinc-assisted mode of substrate binding and catalysis is the hallmark of HolPase. Interestingly, the enzyme-substrate complex structure unveiled that although monomers possess individual catalytic sites they share a common product-exit channel at the dimer interface. Furthermore, target-based screening against HolPase identified several small-molecule inhibitors of this enzyme. Taken together, our study unravels the missing enzyme link in the histidine biosynthesis pathway, augments our current mechanistic understanding of histidine production in , and has helped identify potential inhibitors of this bacterial pathway.