Biology subjects

da Silva, R. G.

Publications and source records attributed to da Silva, R. G..

2 recordsLinked to original sources

bioRxiv2025

Improved nucleoside (2'-deoxy)ribosyltransferases maximize enzyme promiscuity while maintaining catalytic efficiency

Nucleoside analogues have been extensively used to treat viral and bacterial infections and cancer for the past 60 years. However, their chemical synthesis is complex and often requires multiple steps and a dedicated synthetic route for every new nucleoside to be produced. Wild type nucleoside 2'-deoxyribosyltransferase enzymes are promising for biocatalysis. Guided by the structure of the enzyme from the thermophilic organism Chroococcidiopsis thermalis PCC 7203 (CtNDT) bound to the ribonucleoside analogue Immucillin-H, we designed mutants of CtNDT and the psychrotolerant Bacillus psychrosaccharolyticus (BpNDT) to improve catalytic efficiency with 3'-deoxynucleosides and ribonucleosides, while maintaining nucleobase promiscuity to generate over 100 distinct nucleoside products. Enhanced catalytic efficiency towards ribonucleosides and 3'-deoxyribonucleosides occurred via gains in turnover rate, rather than improved substrate binding. We determined crystal structures of two engineered variants as well as kinetic parameters with different substrates, unveiling molecular details underlying their expanded substrate scope. Our rational approach generated robust enzymes and a roadmap for reaction conditions applicable to a wide variety of substrates. Insert Table of Contents artwork here O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=98 SRC="FIGDIR/small/641663v2_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@3ef466org.highwire.dtl.DTLVardef@11f55b0org.highwire.dtl.DTLVardef@32d0dcorg.highwire.dtl.DTLVardef@2e22cc_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2021

Structure, dynamics, and inhibition of Staphylococcus aureus m1A22-tRNA methyltransferase

The enzyme m1A22-tRNA methyltransferase (TrmK) catalyses the transfer of a methyl group from SAM to the N1 of adenine 22 in tRNAs. TrmK is essential for Staphylococcus aureus survival during infection, but has no homologue in mammals, making it a promising target for antibiotic development. Here we describe the structural and functional characterisation of S. aureus TrmK. Crystal structures are reported for S. aureus TrmK apoenzyme and in complexes with SAM and SAH. Isothermal titration calorimetry showed that SAM binds to the enzyme with favourable but modest enthalpic and entropic contributions, whereas SAH binding leads to an entropic penalty compensated by a large favourable enthalpic contribution. Molecular dynamics simulations point to specific motions of the C-terminal domain being altered by SAM binding, which might have implications for tRNA recruitment. Activity assays for S. aureus TrmK-catalysed methylation of WT and position 22 mutants of tRNALeu demonstrate that the enzyme requires an adenine at position 22 of the tRNA. Intriguingly, a small RNA hairpin of 18 nucleotides is methylated by TrmK depending on the position of the adenine. In-silico screening of compounds suggested plumbagin as a potential inhibitor of TrmK, which was confirmed by activity measurements. Furthermore, LC-MS indicated the protein was covalently modified by one equivalent of the inhibitor, and proteolytic digestion coupled with LC-MS identified Cys92, in the vicinity of the SAM-binding site, as the sole residue modified. These results these results identify a cryptic binding pocket of S. aureus TrmK and lay the foundation for future structure-based drug discovery.

biochemistry↗