Allosteric inhibitors of inducible nitric oxide synthase dimerization discovered via combinatorial chemistry

Potent and selective inhibitors of inducible nitric oxide synthase (iNOS) (EC 1.14.13.39) were identified in an encoded combinatorial chemical library that blocked human iNOS dimerization, and thereby NO production. In a cell-based iNOS assay (A-172 astrocytoma cells) the inhibitors had low-nanomolar IC50 values and thus were >1,000-fold more potent than the substrate-based direct iNOS inhibitors 1400W and N-methyl-l-arginine. Biochemical studies confirmed that inhibitors caused accumulation of iNOS monomers in mouse macrophage RAW 264.7 cells. High affinity (Kd ≈ 3 nM) of inhibitors for isolated iNOS monomers was confirmed by using a radioligand binding assay. Inhibitors were >1,000-fold selective for iNOS versus endothelial NOS dimerization in a cell-based assay. The crystal structure of inhibitor bound to the monomeric iNOS oxygenase domain revealed inhibitor–heme coordination and substantial perturbation of the substrate binding site and the dimerization interface, indicating that this small molecule acts by allosterically disrupting protein–protein interactions at the dimer interface. These results provide a mechanism-based approach to highly selective iNOS inhibition. Inhibitors were active in vivo, with ED50 values of <2 mg/kg in a rat model of endotoxin-induced systemic iNOS induction. Thus, this class of dimerization inhibitors has broad therapeutic potential in iNOS-mediated pathologies.

Mendel, a database of nomenclature for sequenced plant genes

The Mendel database contains names for plant-wide families of sequenced plant genes. The names have either been approved by the Commission on Plant Gene Nomenclature (CPGN), an organization of the International Society for Plant Molecular Biology (ISPMB), or are identified as provisional or temporary names. Mendel also identifies the corresponding genes in individual species of plants. Mendel can be searched through the mirror sites at Cornell (http://genome.cornell.edu/cgi-bin/WebAce/webace?db=mendel) and Stanford (http://genome-www.stanford.edu/Mendel/). In addition, parts of Mendel can be downloaded from the CPGN Web site (http://mbclserver.rutgers.edu/CPGN/).