Stagnation in the development of new antibiotics emphasizes the need for the discovery of drugs with novel modes of action that can tackle antibiotic resistance. Contrary to humans, most bacteria use the methylerythritol phosphate (MEP) pathway to synthesize crucial isoprenoid precursors. 1-deoxy-D-xylulose 5-phosphate synthase (DXPS) catalyzes the first and rate-limiting step of the pathway, making it an attractive target. Alkylacetylphosphonates (alkylAPs) are a class of pyruvate mimicking DXPS inhibitors that react with thiamin diphosphate (ThDP) to form a stable phosphonolactyl (PLThDP) adduct. Here, we present the first M. tuberculosis DXPS crystal structure in complex with an inhibitor (butylacetylphosphonate (BAP)) using a construct with improved crystallization properties. The 1.6 Å structure shows that the BAP adduct interacts with catalytically important His40 and several other conserved residues of the active site. In addition, a glycerol molecule, present in the D-glyceraldehyde 3-phosphate (D-GAP) binding site and within 4 Å of the BAP adduct, indicates that there is space to extend and develop more potent alkylAPs. The structure reveals the BAP binding mode and provides insights for enhancing the activity of alkylAPs against M. tuberculosis, aiding in the development of novel antibiotics.

The Zika virus (ZIKV), discovered in Africa in 1947, swiftly spread across continents, causing significant concern due to its recent association with microcephaly in newborns and Guillain-Barré syndrome in adults. Despite a decrease in prevalence, the potential for a resurgence remains, necessitating urgent therapeutic interventions. Like other flaviviruses, ZIKV presents promising drug targets within its replication machinery, notably the NS3 helicase (NS3 ^Hel ) protein, which plays critical roles in viral replication. However, a lack of structural information impedes the development of specific inhibitors targeting NS3 ^Hel . Here we applied high-throughput crystallographic fragment screening on ZIKV NS3 ^Hel , which yielded structures that reveal 3D binding poses of 46 fragments at multiple sites of the protein, including 11 unique fragments in the RNA-cleft site. These fragment structures provide templates for direct design of hit compounds and should thus assist the development of novel direct-acting antivirals against ZIKV and related flaviviruses, thus opening a promising avenue for combating future outbreaks.

The enzyme 1-deoxy-d-xylulose-5-phosphate synthase (DXPS) catalyses the first step of the MEP pathway, a key process for isoprenoid biosynthesis in bacteria that is absent in humans, making it a promising drug target. We present the structure of Mycobacterium tuberculosis DXPS in its apo form, obtained through a soaking method that removes thiamine diphosphate (ThDP) and metals from pre-formed crystals. The apo structure had three regions with absence of electron density near the active site that are unique to the apo form of the enzyme. Comparisons with other homologous DXPS structures highlight a similar dynamic response to cofactor absence. Despite the increased flexibility, key residues for the activity and ThDP binding retain their positions, preserving the structural integrity of the catalytic core. These findings demonstrate the critical role of ThDP in maintaining DXPS stability and suggest that dynamic structural changes in the apo state may influence inhibitor binding targeting the cofactor site.