Evaluation of Pseudomonas aeruginosa Deacetylase LpxC Inhibitory Activity of Dual PDE4−TNFα Inhibitors: A Multiscreening Approach

Synthesis of a tetranitrosyl iron complex with unique structure and properties as an inhibitor of phosphodiesterases

A novel neutral tetranitrosyl iron complex {[Fe(H2O)4]2+[FeR2(NO)2]22-}·4H2O (1) with R = 5-(3-pyridyl)-4H-1,2,4-triazole-3-thiolyls (C7H5N4S), which is a supramolecular ensemble, has been synthesized and studied. As follows from X-ray diffraction analysis, this is an octahedral Fe2+complex (Lewis acid) with two monoanionic dinitrosyl groups [FeR2(NO)2]- (Lewis base) and 4 water molecules as the ligands. As follows from Mössbauer spectra, the coordinating Fe2+ ion is in a low-spin state S = 0, and the dinitrosyl Fe+ ion is in a low-spin state S = 1/2. According to the data of EPR spectroscopy, mass-spectrometry and amperometry, complex 1 in solution forms dinitrosyl particles of [Fe(C7H6N4S-H)2(NO)2]- composition, which are responsible for NO generation. In addition, complex 1 was shown to be a 5-6 times more efficient phosphodiesterase (PDE) inhibitor at 5 × 10-5 M and 10-4 M concentrations than its thioligand. Probable binding sites of the [FeR2(NO)2]- ligand for the bovine PDE1B model have been determined by molecular docking and quantum-chemical calculations.

Small molecule LpxC inhibitors against gram-negative bacteria: Advances and future perspectives

Uridine diphosphate-3-O-(hydroxymyristoyl)-N-acetylglucosamine deacetylase (LpxC) is a metalloenzyme with zinc ions as cofactors and is a key enzyme in the essential structural outer membrane lipid A synthesis commitment step of gram-negative bacteria. As LpxC is extremely homologous among different Gram-negative bacteria, it is conserved in almost all gram-negative bacteria, which makes LpxC a promising target. LpxC inhibitors have been reported extensively in recent years, such as PF-5081090 and CHIR-090 were found to have broad-spectrum antibiotic activity against P. aeruginosa and E. coli. They are mainly classified into hydroxamate inhibitors and non-hydroxamate inhibitors based on their structure, but no LpxC inhibitors have been marketed due to safety and activity issues. This review, therefore, focuses on small molecule inhibitors of LpxC against gram-negative pathogenic bacteria and covers recent advances in LpxC inhibitors, focusing on their structural optimization process, structure-activity relationships, and future directions, with the aim of providing ideas for the development of LpxC inhibitors and clinical research.

Subtractive Genomics, Molecular Docking and Molecular Dynamics Simulation Revealed LpxC as a Potential Drug Target Against Multi-Drug Resistant Klebsiella pneumoniae

The emergence and dissemination of pan drug resistant clones of Klebsiella pneumoniae are great threat to public health. In this regard new therapeutic targets must be highlighted to pave the path for novel drug discovery and development. Subtractive proteomic pipeline brought forth UDP-3-O-[3-hydroxymyristoyl] N-acetylglucosamine deacetylase (LpxC), a Zn⁺² dependent cytoplasmic metalloprotein and catalyze the rate limiting deacetylation step of lipid A biosynthesis pathway. Primary sequence analysis followed by 3-dimensional (3-D) structure elucidation of the protein led to the detection of K. pneumoniae LpxC (KpLpxC) topology distinct from its orthologous counterparts in other bacterial species. Molecular docking study of the protein recognized receptor antagonist compound 106, a uridine-based LpxC inhibitory compound, as a ligand best able to fit the binding pocket with a Gold Score of 67.53. Molecular dynamics simulation of docked KpLpxC revealed an alternate binding pattern of ligand in the active site. The ligand tail exhibited preferred binding to the domain I residues as opposed to the substrate binding hydrophobic channel of subdomain II, usually targeted by inhibitory compounds. Comparison with the undocked KpLpxC system demonstrated ligand induced high conformational changes in the hydrophobic channel of subdomain II in KpLpxC. Hence, ligand exerted its inhibitory potential by rendering the channel unstable for substrate binding.

QSAR models to predict mutagenicity of acrylates, methacrylates and alpha,beta-unsaturated carbonyl compounds

OBJECTIVE

The purpose of this study is to develop a quantitative structure-activity relationship (QSAR) model that can distinguish mutagenic from non-mutagenic species with alpha,beta-unsaturated carbonyl moiety using two endpoints for this activity - Ames test and mammalian cell gene mutation test - and also to gather information about the molecular features that most contribute to eliminate the mutagenic effects of these chemicals.

METHODS

Two data sets were used for modeling the two mutagenicity endpoints: (1) Ames test and (2) mammalian cells mutagenesis. The first one comprised 220 molecules, while the second one 48 substances, ranging from acrylates, methacrylates to alpha,beta-unsaturated carbonyl compounds. The QSAR models were developed by applying linear discriminant analysis (LDA) along with different sets of descriptors computed using the DRAGON software.

RESULTS

For both endpoints, there was a concordance of 89% in the prediction and 97% confidentiality by combining the three models for the Ames test mutagenicity. We have also identified several structural alerts to assist the design of new monomers.

SIGNIFICANCE

These individual models and especially their combination are attractive from the point of view of molecular modeling and could be used for the prediction and design of new monomers that do not pose a human health risk.

Selectivity-based QSAR approach for screening and evaluation of TRH analogs for TRH-R1 and TRH-R2 receptors subtypes

Design and development of therapeutically useful CNS selective thyrotropin-releasing hormone (TRH) analogs acting on TRH-R2 receptor subtype, exerting weak or no TRH-R1-mediated TSH-releasing side effects has gained imagination of researchers in the recent past. The present study reports the development and implementation of a selectivity-based QSAR approach for screening selective agonists of TRH-R2 receptor subtype. The statistically significant predictive models were thoroughly validated using an external validation set whose activity was previously unknown. The model was able to predict preference for either of the receptor subtypes successfully.

Density gradient enrichment of Escherichia coli conditional msbA mutants

Insight into the mechanism of lipid transport to the outer membrane of gram-negative bacteria has been hampered by the lack of an effective genetic screen for defective mutants. This work demonstrates an enrichment of conditional mutants defective in lipopolysaccharide export by Ludox density gradient centrifugation and selection for detergent resistance. New temperature-sensitive mutants with lipid export defects were isolated with single missense mutations in msbA. The results demonstrate the power of this approach for the study of lipid export in Escherichia coli.