RESUMO
In the search for new antibacterial compounds, we repositioned an antimalarial compound class by derivatising it based on the so-called "eNTRy" rules for enhanced accumulation into Gram-negative bacteria. We designed, synthesised and evaluated a small library of amino acid modified compounds together with the respective Boc-protected analogues, leading to no substantial improvement in antibacterial activity against Escherichia coli wild-type K12, whereas more distinct activity differences were observed in E. coli mutant strains ΔtolC, D22, ΔacrB and BL21(DE3)omp8. A comparison of the activity results of the E. coli mutants with respect to the known rules related to enhanced activity against Gram-negative bacteria revealed that applicability of the rules is not always ensured. Out of the four amino acids used in this study, glycine derivatives showed highest antibacterial activity, although still suffering from efflux issues.
RESUMO
A putative open reading frame encoding GTP cyclohydrolase I from Listeria monocytogenes was expressed in a recombinant Escherichia coli strain. The recombinant protein was purified and was confirmed to convert GTP to dihydroneopterin triphosphate (Km = 53â µM; vmax = 180â nmolâ mg-1â min-1). The protein was crystallized from 1.3â M sodium citrate pH 7.3 and the crystal structure was solved at a resolution of 2.4â Å (Rfree = 0.226) by molecular replacement using human GTP cyclohydrolase I as a template. The protein is a D5-symmetric decamer with ten topologically equivalent active sites. Screening a small library of about 9000 compounds afforded several inhibitors with IC50 values in the low-micromolar range. Several inhibitors had significant selectivity with regard to human GTP cyclohydrolase I. Hence, GTP cyclohydrolase I may be a potential target for novel drugs directed at microbial infections, including listeriosis, a rare disease with high mortality.
