Staphylococcus aureus produces large amounts of toxins and virulence factors. In patients with underlying diseases or compromised immune systems, this bacterium can lead to severe infections and ...potentially death. In this study, the crystal structure of the complex of S. aureus lipase (SAL), which is involved in the growth of this bacterium, with petroselinic acid (PSA), an inhibitor of unsaturated fatty acids, was determined by X‐ray crystallography. Recently, PSA was shown to inhibit S. aureus biofilm formation and the enzymatic activity of SAL. To further characterize the inhibitory mechanism, we determined the half‐inhibitory concentration of SAL by PSA and the crystal structure of the complex. The IC50 of the inhibitory effect of PSA on SAL was 3.4 μm. SAL and PSA inhibitors were co‐crystallized, and diffraction data sets were collected to 2.19 Å resolution at SPring‐8 to determine the crystal structure and elucidate the detailed structural interactions. The results show that the fatty acid moiety of PSA is tightly bound to a hydrophobic pocket extending in two directions around the catalytic residue Ser116. Ser116 was also covalently bonded to the carbon of the unsaturated fatty acid moiety, and an oxyanion hole in SAL stabilized the electrons of the double bond. The difference in inhibitory activity between PSA and ester compounds revealed a structure–activity relationship between SAL and PSA. Additional research is required to further characterize the clinical potential of PSA.
Staphylococcus aureus lipase (SAL) is a glycerol ester hydrolase involved in the growth of this bacterium and petroselinic acid (PSA) has been shown to inhibit SAL. In this study, we determined the IC50 of PSA for SAL and the crystal structure of the SAL‐PSA complex. Further research is required to uncover the clinical potential of PSA.
Staphylococcus aureus lipase (SAL), a triacylglycerol esterase, is an important virulence factor and may be a therapeutic target for infectious diseases. Herein, we determined the 3D structure of ...native SAL, the mutated S116A inactive form, and the inhibitor complex using the anti-obesity drug orlistat to aid in drug development. The determined crystal structures showed a typical α/β hydrolase motif with a dimeric form. Fatty acids bound near the active site in native SAL and inactive S116A mutant structures. We found that orlistat potently inhibits SAL activity, and it covalently bound to the catalytic Ser116 residue. This is the first report detailing orlistat-lipase binding. It provides structure-based information on the production of potent anti-SAL drugs and lipase inhibitors. These results also indicated that orlistat can be repositioned to treat bacterial diseases.
Phototropin2 (phot2) is a blue-light (BL) receptor that regulates BL-dependent activities for efficient photosynthesis in plants. phot2 comprises two BL-receiving light-oxygen-voltage–sensing domains ...(LOV1 and LOV2) and a kinase domain. BL-excited LOV2 is thought to be primarily responsible for the BL-dependent activation of the kinase. However, the molecular mechanisms by which small BL-induced conformational changes in the LOV2 domain are transmitted to the kinase remain unclear. Here, we used full-length wild-type and mutant phot2 proteins from Arabidopsis to study their molecular properties in the dark and under BL irradiation. Phosphorylation assays and absorption measurements indicated that the LOV1 domain assists the thermal relaxation of BL-excited LOV2 and vice versa. Using small-angle X-ray scattering and electron microscopy, we observed that phot2 forms a dimer and has a rod shape with a maximum length of 188 Å and a radius of gyration of 44 Å. Under BL, phot2 displayed large conformational changes that bent the rod shape. By superimposing the crystal structures of the LOV1 dimer, LOV2, and a homology model of the kinase to the observed changes, we inferred that the BL-dependent change consisted of positional shifts of both LOV2 and the kinase relative to LOV1. Furthermore, phot2 mutants lacking the photocycle in LOV1 or LOV2 still exhibited conformational changes under BL, suggesting that LOV1 and LOV2 cooperatively contribute to the conformational changes that activate the kinase. These results suggest that BL-activated LOV1 contributes to the kinase activity of phot2. We discuss the possible intramolecular interactions and signaling mechanisms in phot2.
Poly(R)-lactate-co-(R)-3-hydroxybutyrate P(LA-co-3HB) is a biobased polyester with flexible properties efficiently synthesized by engineered Escherichia coli. Here, we aimed at optimizing the ...monomeric composition of the copolymer in terms of its flexibility, and elucidating structural features contributing to their mechanical properties. The LA fraction was successfully regulated in the range of 6–66 mol% by combination of metabolic and enzyme engineering approaches. The copolymers with higher LA fraction showed decreasing melting point from 160 to 125 °C, but increasing glass transition temperature from 7 to 27 °C. Crystallinity of the as-cast film, that was mainly attributed to the crystallization of 3HB unit, also decreased with the increasing LA fraction. Owing to the combined effect of these parameters, the highest elongation to break (approximately 400%), which is comparable to that of polyethylene, was obtained for the copolymers with middle range LA fraction (33 mol%). The high flexibility was maintained in most of the copolymers. Notably, P(21mol%LA-co-3HB) retained its high elongation at break (about 300%) even after storage under ambient condition for 5 months. These results demonstrate that introduction of LA units into the polymer chain effectively and stably inhibited the crystallization of 3HB units.
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•Long-term mechanical stability of microbial P(LA-co-3HB) film was investigated.•P(21mol% LA-co-3HB) maintained elongation at break of ca. 300% after 5 months.•The mechanical stability was ascribed to balancing between crystallinity and Tg.
Quadrupolar interactions of porphyrin bearing two pentafluorophenylethynyl terminals (1) drove the formation of a successive one‐dimensional staircase structure, i.e., J‐aggregates, to yield ...millimeter‐length needles with a single‐crystalline character in methylcyclohexane solution. In contrast, π‐stacked interactions of porphyrin bearing two nonfluorinated phenyl terminals (2) formed no aggregates in solution. A spin‐cast film of 1 also showed bathochromic shift of the Soret and Q bands, indicating the formation of J‐aggregates. The molecular arrangement of the J‐aggregates was revealed by microbeam glazing‐incidence wide‐angle X‐ray diffraction (GIWAXD), and was in good agreement with the optimized structure generated by density functional theory (DFT) calculations.
Complementing aggregates: Successive self‐complementary quadrupolar interactions between pentafluorophenyl and porphyrin rings leads to giant J‐aggregates with a single‐crystalline character up to millimeter‐size, in methylcyclohexane (see scheme).
To investigate a hybrid of isoindigo and thienoisoindigo (TIIG), a new series of unsymmetrical TIIG analogs, in which one of the outer thiophene rings of TIIG is replaced by benzene (CS) or pyridine ...(NS) are prepared. In addition, the π-skeleton extension effects are studied by examining α-substituted TIIG derivatives with thienyl (Dth-TIIG), furyl (Dfu-TIIG), and 1-phenyl-5-pyrazolyl groups (Bis(1-ph-5-py)-TIIG). These materials exhibit ambipolar transistor properties as expected from the energy levels. Dth-TIIG and Dfu-TIIG show hole mobilities exceeding 0.05 cm2 V−1 s−1, and electron mobilities about 0.04 cm2 V−1 s−1, which are close to those of the diphenyl derivative. These molecules are arranged nearly perpendicularly to the substrates in the thin films, and Dth-TIIG has a brickwork-like structure, whereas Dfu-TIIG has uniform columns. CS and Bis(1-ph-5-py)-TIIG have uniform stacking structures, but NS has a dimerized stacking structure due to the slightly bent molecular plane that results from largely unbalanced electron density.
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•A new series of unsymmetrical thienoisoindigo analogs and α-substituted thienoisoindigo derivatives were synthesized.•Crystal structures of these materials and transistor performance were systematically investigated.•Thienyl substituted thienoisoindigo forms brickwork structures, but it has molecular flipping disorder.•This observation suggests possibility of the same kind of disorder in polymers with similar chemical structures.
A strong electron-accepting planar π-conjugated framework, thiadiazole-fused quinoxalineimide (TQI), was designed and synthesized. Three TQI-based small molecules exhibit deep lowest-unoccupied ...molecular orbital (LUMO) levels, which require air stable n-channel conduction (∼−4.0 eV). Among these molecules, Hex-TQI-Br exhibits air-stable n-channel charge transport with a moderate mobility of 0.044 cm2 V–1 s–1.
How is a long strand of genomic DNA packaged into a mitotic chromosome or nucleus? The nucleosome fiber (beads-on-a-string), in which DNA is wrapped around core histones, has long been assumed to be ...folded into a 30-nm chromatin fiber, and a further helically folded larger fiber. However, when frozen hydrated human mitotic cells were observed using cryoelectron microscopy, no higher-order structures that included 30-nm chromatin fibers were found. To investigate the bulk structure of mitotic chromosomes further, we performed small-angle X-ray scattering (SAXS), which can detect periodic structures in noncrystalline materials in solution. The results were striking: no structural feature larger than 11 nm was detected, even at a chromosome-diameter scale (~1 μm). We also found a similar scattering pattern in interphase nuclei of HeLa cells in the range up to ~275 nm. Our findings suggest a common structural feature in interphase and mitotic chromatins: compact and irregular folding of nucleosome fibers occurs without a 30-nm chromatin structure.
Peptides exhibit no melting behavior during heating due to their strong intermolecular hydrogen bonds, which limits the use of peptides as a bulk material. Here, we added a melting point to peptides ...by introducing nylon monomer units via papain-catalyzed chemoenzymatic synthesis. The peptides containing 14 mol% nylon units had a melting point of approximately 200 °C.
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