Cyclothialidine D

Increasing the multi-drug resistance Aeromonas hydrophila creates a health problem regularly thus, an urgent needs to develop and screen potent antibiotics for controlling of the infections. There are many studies have focused on interactions between specific drugs, little is known about the system properties of a full drug interaction in gene network. Thus, an attractive approach for developing novel antibiotics against DNA gyrase, an enzyme essential for DNA replication, transcription, repair and recombination mechanisms which is important for bacterial growth and cell division. Homology modeling method was used to generate the 3-D structure of B subunit of DNA gyrase (gyrB) using known crystal structure. The active amino acids in 3-D structure of gyrB were targeted for structure based virtual screening of potent drugs by molecular docking. Number of drugs and analogs were selected and used for docking against gryB. The drugs Cinodine I, Cyclothialidine and Novobiocin were found to be more binding affinity with gyrB-drug interaction. The homology of gyrB protein sequence of A. hydrophila resembles with other species of Aeromonas closely showed relationship in phylogenetic tree. We have also demonstrated the gene network interactions of gyrB with other cellular proteins which are playing the key role in gene regulation. These findings provide new insight to understand the 3-D structure of gyrB which can be used in structure-based drug discovery; and development of novel, potent and specific drug against B subunit of DNA gyrase.

Chemical transmission between neurons and glial cells is an important element of integration in the CNS. Here, we describe currents activated by NMDA in cortical astrocytes, identified in transgenic mice that express enhanced green fluorescent protein under control of the human glial fibrillary acidic protein promoter. Astrocytes were studied by whole-cell voltage clamp either in slices or after gentle nonenzymatic mechanical dissociation. Acutely isolated astrocytes showed a three-component response to glutamate. The initial rapid component was blocked by 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide (NBQX), which is an antagonist of AMPA receptors (IC50, 2 microM), and the NMDA receptor antagonist D-AP-5 blocked the later sustained component (IC50, 0.6 microM). The third component of glutamate application response was sensitive to D,L-threo-beta-benzyloxyaspartate, a glutamate transporter blocker. Fast application of NMDA evoked concentration-dependent inward currents (EC50, 0.3 microM); these showed use-dependent block by (+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine maleate (MK-801). These NMDA-evoked currents were linearly dependent on membrane potential and were not affected by extracellular magnesium at concentrations up to 10 mM. Electrical stimulation of axons in layer IV-VI induced a complex inward current in astrocytes situated in the cortical layer II, part of which was sensitive to MK-801 at holding potential -80 mV and was not affected by the AMPA glutamate receptor antagonist NBQX. The fast miniature spontaneous currents were observed in cortical astrocytes in slices as well. These currents exhibited both AMPA and NMDA receptor-mediated components. We conclude that cortical astrocytes express functional NMDA receptors that are devoid of Mg2+ block, and these receptors are involved in neuronal-glial signal transmission.

DNA gyrase is an attractive and well established target for the development of antibacterial agents. This bacterial enzyme, whose biological function is to control the topological state of DNA molecules, consists of two catalytic subunits; GyrA is responsible for DNA breakage and reunion, while the subunit GyrB contains the ATP-binding site. Coumarins and cyclothialidines are natural products that inhibit the ATPase activity of DNA gyrase by blocking the binding of ATP to subunit GyrB. The mechanism of action of these compounds was exhaustively characterized by biochemical methods and supported by protein crystallography. The abundance of crystallographic data on the N-terminal domain of GyrB in its complexes with various ligands has enabled the structure-based design of novel efficient chemotypes as inhibitors of the ATPase domain. This review summarizes the discovery of ATPase inhibitors of DNA gyrase B in the last decade and their development as potential antibacterial agents.