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Protein kinase CK2 is associated with a number of human diseases, among them cancer, and is therefore a target for inhibitor development in industry and academia. Six crystal structures of either CK2α, the catalytic subunit of human protein kinase CK2, or its paralog CK2α' in complex with two ATP-competitive inhibitors-based on either a flavonol or a thieno[2,3-d]pyrimidine framework-are presented. The structures show examples for extreme structural deformations of the ATP-binding loop and its neighbourhood and of the hinge/helix αD region, i.e., of two zones of the broader ATP site environment. Thus, they supplement our picture of the conformational space available for CK2α and CK2α'. Further, they document the potential of synthetic ligands to trap unusual conformations of the enzymes and allow to envision a new generation of inhibitors that stabilize such conformations. [ABSTRACT FROM AUTHOR]

ABSTRACT Leucyl‐tRNA synthetase (LeuRS) is clinically validated molecular target for antibiotic development. Recently, we have reported several classes of small‐molecular inhibitors targeting aminoacyl‐adenylate binding site of Mycobacterium tuberculosis LeuRS with antibacterial activity. In this work, we performed in silico site‐directed mutagenesis of M. tuberculosis LeuRS synthetic site in order to identify the most critical amino acid residues for the interaction with substrate and prove binding modes of inhibitors. We carried out 20‐ns molecular dynamics (MD) simulations and used umbrella sampling (US) method for the calculation of the binding free energy (ΔGb) of leucyl‐adenylate with wild‐type and mutated forms of LeuRS. According to molecular modeling results, it was found that His89, Tyr93, and Glu660 are essential amino acid residues both for aminoacyl‐adenylate affinity and hydrogen bond formation. We have selected His89 for experimental site‐directed mutagenesis since according to our previous molecular docking results this amino acid residue was predicted to be important for inhibitor interaction in adenine‐binding region. We obtained recombinant mutant M. tuberculosis LeuRS H89A. Using aminoacylation assay we have found that the mutation of His89 to Ala in the active site of M. tuberculosis LeuRS results in significant decrease of inhibitory activity for compounds belonging to three different chemical classes—3‐phenyl‐5‐(1‐phenyl‐1H‐[1,2,3]triazol‐4‐yl)‐[1,2,4]oxadiazoles, N‐benzylidene‐N′‐thiazol‐2‐yl‐hydrazines, and 1‐oxo‐1H‐isothiochromene‐3‐carboxylic acid (4‐phenyl‐thiazol‐2‐yl)‐amide derivatives. Therefore, the interaction with His89 should be taken into account during further M. tuberculosis LeuRS inhibitors development and optimization. [ABSTRACT FROM AUTHOR]

Abstract: The influence of methyl-, 2-hydroxyethyl-, dimethyl-, diethyl- and benzoyl-amino substituents in the 6,6′-positions of benzothiazole heterocycle of trimethine cyanines on their spectral-luminescent properties and behavior in presence of DNA, RNA and BSA was studied. It was shown that incorporation of 6,6′-substituents generally leads to the increase in dyes tendency to aggregation, resulting in the considerable decrease in the emission intensity of the disubstituted dyes as compared to the unsubstituted ones. Emission of the studied 6,6′-disubstited dyes in DNA presence is considerably more intensive than in presence of RNA, that points on the existing of DNA binding preference for the mentioned dyes. Insertion of benzoyl-amino groups into the 6,6′-positions permitted us to design the DNA-sensitive dyes on the basis of symmetric trimethine cyanines with unsubstituted polymethine chain, while typically such dyes slightly respond on the presence of biopolymers. 6,6′-Benzoyl-amino-disubstituted trimethine cyanines are proposed as efficient dyes for DNA detection. [Copyright &y& Elsevier]