Discovery of Mdm2-MdmX E3 ligase inhibitors using a cell-based ubiquitination assay.

E3 ubiquitin ligases are of interest as drug targets for their ability to regulate protein stability and function. The oncogene Mdm2 is an attractive E3 ligase to target, as it is the key negative regulator of the tumor suppressor p53, which controls the transcription of genes involved in cell fate. Overexpression of Mdm2 facilitates tumorigenesis by inactivating p53, and through p53-independent oncogenic effects.

Allosteric site variants of Haemophilus influenzae beta-carbonic anhydrase.

Haemophilus influenzae beta-carbonic anhydrase (HICA) is hypothesized to be an allosteric protein that is regulated by the binding of bicarbonate ion to a non-catalytic (inhibitory) site that controls the ligation of Asp44 to the catalytically essential zinc ion. We report here the X-ray crystallographic structures of two variants (W39F and Y181F) involved in the binding of bicarbonate ion in the non-catalytic site and an active-site variant (D44N) that is incapable of forming a strong zinc ligand. The alteration of Trp39 to Phe increases the apparent K(i) for bicarbonate inhibition by 4.

Ligand sensitivity in dimeric associations of the serotonin 5HT2c receptor.

G-protein-coupled receptors (GPCRs) respond to external stimuli by activating heterotrimeric G proteins inside the cell. There is increasing evidence that many GPCRs exist as dimers or higher oligomers, but the biochemical nature of such dimers and what roles they have, if any, in signal transduction remains unclear. We conducted a comprehensive study of dimerization of the 5HT2c serotonin receptor using disulphide-trapping experiments.

Enzyme annotation with chemical tools.

Defining the activity of an enzyme in a cell-based system is preferable to in vitro biochemical techniques requiring extensive purification. Chiang et al. use small molecules, RNA interference, and metabolomics to characterize a novel enzyme upregulated in cancer cells.