Cyclic GMP-AMP synthase (cGAS) is a cytosolic DNA sensor mediating innate antimicrobial immunity. It catalyzes the synthesis of a noncanonical cyclic dinucleotide 2′,5′ cGAMP that binds to STING and mediates the activation of TBK1 and IRF-3. Activated IRF-3 translocates to the nucleus and initiates the transcription of the IFN-β gene. The structure of mouse cGAS bound to an 18 bp dsDNA revealed that cGAS interacts with dsDNA through two binding sites, forming a 2:2 complex. Enzyme assays and IFN-β reporter assays of cGAS mutants demonstrated that interactions at both DNA binding sites are essential for cGAS activation. Mutagenesis and DNA binding studies showed that the two sites bind dsDNA cooperatively and site B plays a critical role in DNA binding. The structure of mouse cGAS bound to dsDNA and 2′,5′ cGAMP provided insight into the catalytic mechanism of cGAS. These results demonstrated that cGAS is activated by dsDNA-induced oligomerization.

Histone H3-lysine79 (H3K79) methyl transferase DOT1L plays critical roles in normal cell differentiation as well as initiation of acute leukemia. We used structure and mechanism based design to discover several potent inhibitors of DOT1L with IC50 values as low as 38 nM. These inhibitors exhibit only weak or no activities against four other representative histone lysine and arginine methyltransferases, G9a, SUV39H1, PRMT1 and CARM1. The x-ray crystal structure of a DOT1L:inhibitor complex reveals that N6-methyl group of the inhibitor, located favorably in a predominantly hydrophobic cavity of DOT1L, provides the observed high selectivity. Structural analysis shows that it will disrupt at least one H-bond and/or have steric repulsion for other histone methyltransferases. These compounds represent novel chemical probes for biological function studies of DOT1L in health and disease.

1-Deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) is a novel target for developing new antibacterial (including anti-tuberculosis) and antimalaria drugs. 41 lipophilic phosphonates, representing a new class of DXR inhibitors, were synthesized, among which 5-phenylpyridin-2-ylmethylphosphonic acid possesses the most activity against E. coli DXR (EcDXR) with a Ki of 420 nM. Structure activity relationships (SAR) are discussed, which can be rationalized using our EcDXR:inhibitor structures, and a predictive quantitative SAR (QSAR) model is also developed. Since inhibition studies of DXR from Mycobacterium tuberculosis (MtDXR) have not been well performed, 48 EcDXR inhibitors with a broad chemical diversity were found, however, to generally exhibit considerably reduced activity against MtDXR. The crystal structure of a MtDXR:inhibitor complex reveals the flexible loop containing the residues 198–208 has no strong interactions with the 3,4-dichlorophenyl group of the inhibitor, representing a structural basis for the reduced activity. Overall, these results provide implications in the future design and development of potent DXR inhibitors.

1-Deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) in the non-mevalonate isoprene biosynthesis pathway is a target for developing antimalarial drugs. Fosmidomycin, a potent DXR inhibitor, showed safety as well as efficacy against P. falciparum malaria in clinical trials. Based on our previous quantitative structure activity relationship (QSAR) and crystallographic studies, several novel pyridine-containing fosmidomycin derivatives were designed, synthesized and found to be highly potent inhibitors of P. falciparum DXR (PfDXR) having Ki values of 1.9 – 13 nM, with the best one being ~11× more active than fosmidomycin. These compounds also potently block the proliferation of multi-drug resistant P. falciparum with EC50 values as low as 170 nM. A 2.3 Å crystal structure of PfDXR in complex with one of the inhibitors is reported, showing the flexible loop of the protein undergoes conformational changes upon ligand binding and a hydrogen bond and favorable hydrophobic interactions between the pyridine group and PfDXR account for the enhanced activity.

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Structures of porcine insulin crystals soaked in 1 M sodium sulfate at pH 5.00, 5.53, 5.80, 6.00, 6.16, 6.26, 6.35, 6.50, 6.98 and 9.00 have been determined at between 1.7 and 1.9 A resolution. GluB13 exhibits a single conformation at pH

Mitochondrial dysfunction is essential in the development and prognosis of diabetic cardiomyopathy (DCM). Resveratrol (RES) is thought as a mitochondrial protector. In this study, we hypothesized that RES may ameliorate mitochondrial function and consequently improve cardiac function in diabetic rats, and uncoupling protein 2 (UCP2) was involved in the protective effects of RES on DCM. Thirty rats were divided into three groups: normal control, DCM, and DCM+RES groups. DCM was induced by high-fat diet and streptozotocin (STZ) intraperitoneal injection, the rats in DCM+RES group received RES gavage for 16 weeks. RES improved the insulin resistance, and reduced the level of triglyceride, cholesterol, and low density lipoprotein cholesterol (LDLc) in DCM rats (all P < 0.05). Echocardiographic and hemodynamic studies revealed that RES treatment reversed the impaired diastolic and systolic cardiac function in DCM rats. Meanwhile, RES improved myocardial structural disorder and fibrosis, reserved mitochondrial membrane potential level (P < 0.05), and suppressed myocardial apoptosis in DCM rats (P < 0.05). Myocardial mitochondrial respiratory enzyme activities were improved by RES treatment in DCM rats (P < 0.05), accompanied with attenuated reactive oxygen species (ROS) generation (P < 0.05). The expression of UCP2 was further increased by RES treatment both in the myocardium of DCM rats (P < 0.05) and in the H9c2 cardiomyocytes incubated with high-glucose (P < 0.05). The protective effects of RES on high glucose-induced ROS generation, MPTP opening, Cyto c release, and cell apoptosis were all blunted by inhibiting the expression of UCP2 (all P < 0.05). In conclusion, RES treatment improved cardiac function and inhibited cardiomyocyte apoptosis, involving in ameliorating mitochondrial function in diabetic rats. UCP2 mediated the protective effects of RES on diabetic hearts.