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In the 1990s, an uncommonly high percentage of glutathione S-transferase M1 (GSTM1) negative bladder cancer cases (70%) was reported in the greater Dortmund area. The question arose as to whether this uncommonly high percentage of GSTM1 negative bladder cancer cases was due to environmental and/or occupational exposure decades ago. Thus, 15 years later, another study on bladder cancer was performed in the same area after the coal, iron, and steel industries had finally closed in the 1990s. In total 196 bladder cancer patients from the St.-Josefs-Hospital Dortmund-Hörde and 235 controls with benign urological diseases were assessed by questionnaire and genotyped for GSTM1, glutathione S-transferase T1 (GSTT1), and the N-acetyltransferase 2 (NAT2) tag SNP rs1495741. The frequency of the GSTM1 negative genotype was 52% in bladder cancer cases and thus lower compared to a previous study performed from 1992 to 1995 in the same area (70%). NAT2 genotypes were distributed equally among cases and controls (63% slow acetylators). Fewer GSTT1 negative genotypes were present in cases (17%) than in controls (20%).

Carotenoids protect the photosynthetic apparatus against harmful radicals arising from the presence of both light and oxygen. They also act as accessory pigments for harvesting solar energy, and are required for stable assembly of many light-harvesting complexes. In the phototrophic bacterium Rhodobacter (Rba.) sphaeroides phytoene desaturase (CrtI) catalyses three sequential desaturations of the colourless carotenoid phytoene, extending the number of conjugated carbon-carbon double bonds, N, from three to nine and producing the yellow carotenoid neurosporene; subsequent modifications produce the yellow/red carotenoids spheroidene/spheroidenone (N=10/11). Genomic crtI replacements were used to swap the native three-step Rba. sphaeroides CrtI for the four-step Pantoea agglomerans enzyme, which re-routed carotenoid biosynthesis and culminated in the production of 2,2'-diketo-spirilloxanthin under semi-aerobic conditions. The new carotenoid pathway was elucidated using a combination of HPLC and mass spectrometry. Premature termination of this new pathway by inactivating crtC or crtD produced strains with lycopene or rhodopin as major carotenoids. All of the spirilloxanthin series carotenoids are accepted by the assembly pathways for LH2 and RC-LH1-PufX complexes. The efficiency of carotenoid-to-bacteriochlorophyll energy transfer for 2,2'-diketo-spirilloxanthin (15 conjugated C = C bonds; N=15) in LH2 complexes is low, at 35%. High energy transfer efficiencies were obtained for neurosporene (N=9; 94%), spheroidene (N=10; 96%) and spheroidenone (N=11; 95%), whereas intermediate values were measured for lycopene (N=11; 64%), rhodopin (N=11; 62%) and spirilloxanthin (N=13; 39%). The variety and stability of these novel Rba. sphaeroides antenna complexes make them useful experimental models for investigating the energy transfer dynamics of carotenoids in bacterial photosynthesis.

Alcohol is a well-known risk factor for hepatocellular carcinoma. Autophagy plays a dual role in liver cancer, as it suppresses tumor initiation and promotes tumor progression. Transcription factor EB (TFEB) is a master regulator of lysosomal biogenesis and autophagy, which is impaired in alcohol-related liver disease. However, the role of TFEB in alcohol-associated liver carcinogenesis is unknown. Liver-specific Tfeb knockout (KO) mice and their matched wild-type (WT) littermates were injected with the carcinogen diethylnitrosamine (DEN), followed by chronic ethanol feeding. The numbers of both total and larger tumors increased significantly in DEN-treated mice fed ethanol diet than in mice fed control diet. Although the number of tumors was not different between WT and L-Tfeb KO mice fed either control or ethanol diet, the number of larger tumors was less in L-Tfeb KO mice than in WT mice. No differences were observed in liver injury, steatosis, inflammation, ductular reaction, fibrosis, and tumor cell proliferation in DEN-treated mice fed ethanol. However, the levels of glypican 3, a marker of malignant hepatocellular carcinoma, markedly decreased in DEN-treated L-Tfeb KO mice fed ethanol in comparison to the WT mice. These findings indicate that chronic ethanol feeding promotes DEN-initiated liver tumor development, which is attenuated by genetic deletion of hepatic TFEB.

AbstractChallenging environments have guided nature in the development of ultrastable protein complexes. Specialized bacteria produce discrete multi-component protein networks called cellulosomes to effectively digest lignocellulosic biomass. While network assembly is enabled by protein interactions with commonplace affinities, we show that certain cellulosomal ligand–receptor interactions exhibit extreme resistance to applied force. Here, we characterize the ligand–receptor complex responsible for substrate anchoring in the Ruminococcus flavefaciens cellulosome using single-molecule force spectroscopy and steered molecular dynamics simulations. The complex withstands forces of 600–750 pN, making it one of the strongest bimolecular interactions reported, equivalent to half the mechanical strength of a covalent bond. Our findings demonstrate force activation and inter-domain stabilization of the complex, and suggest that certain network components serve as mechanical effectors for maintaining network integrity. This detailed understanding of cellulosomal network components may help in the development of biocatalysts for production of fuels and chemicals from renewable plant-derived biomass.

The nonheme diiron enzyme cyanobacterial aldehyde deformylating oxygenase, cADO, catalyzes the highly unusual deformylation of aliphatic aldehydes to alkanes and formate. We have determined crystal structures for the enzyme with a long-chain water-soluble aldehyde and medium-chain carboxylic acid bound to the active site. These structures delineate a hydrophobic channel that connects the solvent with the deeply buried active site and reveal a mode of substrate binding that is different from previously determined structures with long-chain fatty acids bound. The structures also identify a water channel leading to the active site that could facilitate the entry of protons required in the reaction. NMR studies examining 1-[(13)C]-octanal binding to cADO indicate that the enzyme binds the aldehyde form rather than the hydrated form. Lastly, the fortuitous cocrystallization of the metal-free form of the protein with aldehyde bound has revealed protein conformation changes that are involved in binding iron.

Cyanobacterial aldehyde decarbonylase (cAD) is a non-heme diiron oxygenase that catalyzes the conversion of fatty aldehydes to alkanes and formate. The mechanism of this chemically unusual reaction is poorly understood. We have investigated the mechanism of C1-C2 bond cleavage by cAD using a fatty aldehyde that incorporates a cyclopropyl group, which can act as a radical clock. When reacted with cAD, the cyclopropyl aldehyde produces 1-octadecene as the rearranged product, providing evidence for a radical mechanism for C-C bond scission. In an alternate pathway, the cyclopropyl aldehyde acts as a mechanism-based irreversible inhibitor of cAD through covalent binding of the alkyl chain to the enzyme.

AbstractMicroalgae are unicellular photosynthetic organisms considered as potential alternative sources for biomass, biofuels or high value products. However, their limited biomass productivity represents a bottleneck that needs to be overcome to meet the applicative potential of these organisms. One of the domestication targets for improving their productivity is the proper balance between photoprotection and light conversion for carbon fixation. In the model organism for green algae, Chlamydomonas reinhardtii, a photoprotective mechanism inducing thermal dissipation of absorbed light energy, called Non-photochemical quenching (NPQ), is activated even at relatively low irradiances, resulting in reduced photosynthetic efficiency. Two pigment binding proteins, LHCSR1 and LHCSR3, were previously reported as the main actors during NPQ induction in C. reinhardtii. While previous work characterized in detail the functional properties of LHCSR3, few information is available for the LHCSR1 subunit. Here, we investigated in vitro the functional properties of LHCSR1 and LHCSR3 subunits: despite high sequence identity, the latter resulted as a stronger quencher compared to the former, explaining its predominant role observed in vivo. Pigment analysis, deconvolution of absorption spectra and structural models of LHCSR1 and LHCR3 suggest that different quenching efficiency is related to a different occupancy of L2 carotenoid binding site.