The crystal structures of the human androgen receptor (hAR) and human progesterone receptor ligandbinding domains in complex with the same ligand metribolone (R1881) have been determined. Both threedimensional structures show the typical nuclear receptor fold. The change of two residues in the ligandbinding pocket between the human progesterone receptor and hAR is most likely the source for the specificity of R1881 to the hAR. The structural implications of the 14 known mutations in the ligand-binding pocket of the hAR ligand-binding domains associated with either prostate cancer or the partial or complete androgen receptor insensitivity syndrome were analyzed. The effects of most of these mutants could be explained on the basis of the crystal structure. Androgen (AR)1 and progesterone receptors (PR) are members of the superfamily of nuclear receptors that includes the steroid receptors, among others, as well as the vitamin D, thyroid, retinoic acid receptors, and the so-called orphan receptors. In addition, AR and PR are members of a group of four closely related steroid receptors including the mineralocorticoid receptor and the glucocorticoid receptor recognizing the same hormone response element. In general, steroid receptors are comprised of five to six domains and act as ligand-activated transcription factors that control the expression of specific genes. To date, no experimentally determined three-dimensional structure is available for a complete receptor. During the past few years, x-ray structures have been published for two of the domains, the DNA-binding domain as well as for a number of ligand-binding domains (LBD) including LBD⅐ligand complexes of the estrogen receptor ␣ and ␤, the PR, the vitamin D receptor, the retinoic acid receptors (X,RXR; acid, RAR), the thyroid hormone receptor, and the peroxisome proliferatoractivated receptors (1-13). Despite the low sequence homology of as low as 20% between the LBDs of different nuclear receptor families, all these proteins share a similar fold. They are comprised of up to 12 helices and a small ␤-sheet arranged in a so-called ␣-helical sandwich, a kind of fold that up to now has only been observed for the LBDs of nuclear receptors. Depending on the nature of the bound ligand, agonist, or antagonist, the carboxyl-terminal helix H12 is found in either one of two orientations. In the agonist-bound conformation, helix H12 serves as a "lid" to close the ligand-binding pocket (LBP), whereas in the antagonist-bound conformation helix H12 is positioned in a different orientation thus opening the entrance to the LBP.Androgens and their receptors play an important role in male physiology and pathology.

Over the past 25 years, biophysical technologies such as X-ray crystallography, nuclear magnetic resonance spectroscopy, surface plasmon resonance spectroscopy and isothermal titration calorimetry have become key components of drug discovery platforms in many pharmaceutical companies and academic laboratories. There have been great improvements in the speed, sensitivity and range of possible measurements, providing high-resolution mechanistic, kinetic, thermodynamic and structural information on compound-target interactions. This Review provides a framework to understand this evolution by describing the key biophysical methods, the information they can provide and the ways in which they can be applied at different stages of the drug discovery process. We also discuss the challenges for current technologies and future opportunities to use biophysical methods to solve drug discovery problems.

Members of the KDM5 (also known as JARID1) family are 2-oxoglutarate- and Fe(2+)-dependent oxygenases that act as histone H3K4 demethylases, thereby regulating cell proliferation and stem cell self-renewal and differentiation. Here we report crystal structures of the catalytic core of the human KDM5B enzyme in complex with three inhibitor chemotypes. These scaffolds exploit several aspects of the KDM5 active site, and their selectivity profiles reflect their hybrid features with respect to the KDM4 and KDM6 families. Whereas GSK-J1, a previously identified KDM6 inhibitor, showed about sevenfold less inhibitory activity toward KDM5B than toward KDM6 proteins, KDM5-C49 displayed 25-100-fold selectivity between KDM5B and KDM6B. The cell-permeable derivative KDM5-C70 had an antiproliferative effect in myeloma cells, leading to genome-wide elevation of H3K4me3 levels. The selective inhibitor GSK467 exploited unique binding modes, but it lacked cellular potency in the myeloma system. Taken together, these structural leads deliver multiple starting points for further rational and selective inhibitor design.

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The longest part of the sperm flagellum, the principal piece, contains the fibrous sheath, a cytoskeletal element unique to spermiogenesis. We performed mass spectrometry proteomics on isolated human fibrous sheaths identifying a unique ADP/ATP carrier protein, SFEC [AAC4], seven glycolytic enzymes previously unreported in the human sperm fibrous sheath, and sorbitol dehydrogenase. SFEC, pyruvate kinase and aldolase were co-localized by immunofluorescence to the principal piece. A homology model constructed for SFEC predicted unique residues at the entrance to the nucleotide binding pocket of SFEC that are absent in other human ADP/ATP carriers, suggesting opportunities for selective drug targeting. This study provides the first evidence of a role for an ADP/ATP carrier family member in glycolysis. The co-localization of SFEC and glycolytic enzymes in the fibrous sheath supports a growing literature that the principal piece of the flagellum is capable of generating and regulating ATP independently from mitochondrial oxidation in the mid-piece. A model is proposed that the fibrous sheath represents a highly ordered complex, analogous to the electron transport chain, in which adjacent enzymes in the glycolytic pathway are assembled to permit efficient flux of energy substrates and products with SFEC serving to mediate energy generating and energy consuming processes in the distal flagellum, possibly as a nucleotide shuttle between flagellar glycolysis, protein phosphorylation and mechanisms of motility.