Antibiotic 2-11-A

Enoyl-ACP reductase, the last enzyme of the fatty-acid biosynthetic pathway, is the molecular target for several successful antibiotics such as the tuberculosis therapeutic isoniazid. It is currently under investigation as a narrow-spectrum antibiotic target for the treatment of several types of bacterial infections. The diazaborine family is a group of boron heterocycle-based synthetic antibacterial inhibitors known to target enoyl-ACP reductase. Development of this class of molecules has thus far focused solely on the sulfonyl-containing versions. Here, the requirement for the sulfonyl group in the diazaborine scaffold was investigated by examining several recently characterized enoyl-ACP reductase inhibitors that lack the sulfonyl group and exhibit additional variability in substitutions, size and flexibility. Biochemical studies are reported showing the inhibition of Escherichia coli enoyl-ACP reductase by four diazaborines, and the crystal structures of two of the inhibitors bound to E. coli enoyl-ACP reductase solved to 2.07 and 2.11 Å resolution are reported. The results show that the sulfonyl group can be replaced with an amide or thioamide without disruption of the mode of inhibition of the molecule.

Pseudomonas aeruginosa is an increasingly antibiotic-resistant pathogen that causes severe lung infections, burn wound infections, and diabetic foot infections. P. aeruginosa produces the siderophore pyochelin through the use of a non-ribosomal peptide synthetase (NRPS) biosynthetic pathway. Targeting members of siderophore NRPS proteins is one avenue currently under investigation for the development of new antibiotics against antibiotic-resistant organisms. Here, the crystal structure of the pyochelin adenylation domain PchD is reported. The structure was solved to 2.11 Å when co-crystallized with the adenylation inhibitor 5'-O-(N-salicylsulfamoyl)adenosine (salicyl-AMS) and to 1.69 Å with a modified version of salicyl-AMS designed to target an active site cysteine (4-cyano-salicyl-AMS). In the structures, PchD adopts the adenylation conformation, similar to that reported for AB3403 from Acinetobacter baumannii.

Regulators belonging to multiple antibiotic resistance regulator (MarR) family are widespread in prokaryotes and are involved in regulation of genes that are responsible for virulence and pathogenicity in most of the clinically important pathogens. Here we report the transcriptional, biophysical, and X-ray analyses of homologue of SlyA (HosA), a member of MarR family that is predominantly present in the pathogenic strains of Enterobacteriaceae family. The initiation of hosA transcription was observed to occur at two independent start sites and subsequent binding study has revealed that the purified HosA interacts with its upstream region suggesting a probable autoregulation. The secondary structure analysis through circular dichroism spectroscopy demonstrated that HosA is predominantly composed of the alpha helix with higher thermal stability. To further understand the three-dimensional structure, HosA was crystallized and the crystals were diffracted to maximum of 2.9 Ǻ on exposure to X-rays. Analysis of the X-ray crystallographic data suggested a primitive space group (P 6 ? 2 2), with unit cell parameters a = b = 64.19 Å and c = 244.25 Å. The solvent content and Matthews coefficient were 41 % and 2.11 Å(3) Da(-1), respectively, which indicated the existence of two molecules of HosA in the asymmetric unit of crystal.