Monoacylglycerol lipases (MGLs) catalyse the hydrolysis of monoacylglycerol into free fatty acid and glycerol. MGLs have been identified throughout all genera of life and have adopted different substrate specificities depending on their physiological role. In humans, MGL plays an integral part in lipid metabolism affecting energy homeostasis, signalling processes and cancer cell progression. In bacteria, MGLs degrade short-chain monoacylglycerols which are otherwise toxic to the organism. We report the crystal structures of MGL from the bacterium Bacillus sp. H257 (bMGL) in its free form at 1.2 Å and in complex with phenylmethylsulfonyl fluoride at 1.8 Å resolution. In both structures, bMGL adopts an α/β hydrolase fold with a cap in an open conformation. Access to the active site residues, which were unambiguously identified from the protein structure, is facilitated by two different channels. The larger channel constitutes the highly hydrophobic substrate binding pocket with enough room to accommodate monoacylglycerol. The other channel is rather small and resembles the proposed glycerol exit hole in human MGL. Molecular dynamics simulation of bMGL yielded open and closed states of the entrance channel and the glycerol exit hole. Despite differences in the number of residues, secondary structure elements, and low sequence identity in the cap region, this first structure of a bacterial MGL reveals striking structural conservation of the overall cap architecture in comparison with human MGL. Thus it provides insight into the structural conservation of the cap amongst MGLs throughout evolution and provides a framework for rationalising substrate specificities in each organism.

It was demonstrated that the interaction of the aminoacridizinium salts 2a-2d with DNA depends on the substitution pattern of the chromophore. Spectrophotometric and fluorometric titrations of the acridizinium salts 2a-2d with natural and synthetic polynucleotides reveal that the degree of interaction of the acridizinium salts 2a-2d with the nucleic acid differs significantly. The binding mode of the dyes with DNA was evaluated by circular dichroism and linear dichroism spectroscopy and compared with the parent system 2c. Whereas the 9-aminoacridizinium (2a) mainly intercalates into DNA, the salts 2b-c show a higher degree of association to the DNA backbone. The intercalated aminoacridizinium 2a caused few strand breaks upon UVA exposure, whereas the salts 2b-2d exhibit relatively efficient DNA-damaging properties. All acridizinium salts showed a sequence-selective strand cleavage for guanine-rich DNA regions.

In addition to uracil, the noncanonical nucleobases xanthine and hypoxanthine are important lesions that are formed from the canonical bases when a cell is under oxidative stress. It is known that they lead to point mutations; however, more detailed information about their ability to form hydrogen-bonded complexes is not available. In the present paper such information is obtained by a combined experimental and theoretical approach. Accurate association constants of xanthosine and inosine dimers are determined by concentration dependent 1H NMR experiments, and a structural characterization of individual complexes formed in solution is performed through measurements under slow exchange conditions at very low temperatures. An interpretation of the experimental data concerning complex geometries becomes possible through a comparison of measured and computed NMR chemical shifts. Further qualitative insights into the hydrogen bonding abilities of xanthine and hypoxanthine are obtained by a theoretical characterization of all possible pairing modes of xanthine and hypoxanthine dimers and by a comparison with simplified model systems. The influence of a polar medium on the bonding properties is also estimated and the importance of the various effects is discussed. Our analysis shows to what extent secondary electronic and electrostatic effects influence the hydrogen bonding properties of xanthine and hypoxanthine in the gas phase and in polar solvents.

The protein Yju3p is the orthologue of monoglyceride lipases in the yeastSaccharomyces cerevisiae. A soluble variant of this lipase termed s-Yju3p (38.3 kDa) was generated and purified to homogeneity by affinity and size-exclusion chromatography. s-Yju3p was crystallized in a vapour-diffusion setup at 293 K and a complete data set was collected to 2.4 Å resolution. The crystal form was orthorhombic (space groupP212121), with unit-cell parametersa= 77.2,b= 108.6,c= 167.7 Å. The asymmetric unit contained four molecules with a solvent content of 46.4%.