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101.
An NAD+-dependent l-arabinitol 4-dehydrogenase (LAD, EC 1.1.1.12) from Neurospora crassa was cloned and expressed in Escherichia coli and purified to homogeneity. The enzyme was a homotetramer and contained two Zn2+ ions per subunit, displaying similar characteristics to medium-chain sorbitol dehydrogenases (SDHs). High enzymatic activity
was observed for substrates l-arabinitol, adonitol, and xylitol and no activity for d-mannitol, d-arabinitol, or d-sorbitol. The enzyme showed strong preference for NAD+ but also displayed a very low yet detectable activity with NADP+. Mutational analysis of residue F59, the single different substrate-binding residue between LADs and d-SDHs, failed to confer the enzyme the ability to accept d-sorbitol as a substrate, suggesting that the amino acids flanking the active site cleft may be responsible for the different
activity and affinity patterns between LADs and SDHs. This enzyme should be useful for in vivo and in vitro production of
xylitol and ethanol from l-arabinose.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
102.
Differential accumulation of proteinase inhibitor I in normal and crown gall tissue of tobacco, tomato, and potato 下载免费PDF全文
A proteinase inhibitor (inhibitor I) is induced in crown gall tumors of tobacco (Nicotiana tabacum) initiated through infection with the tumorinducing bacterium, Agrobacterium tumefaciens, strains B6 or CG-14. Uninfected tissues do not contain immunologically detectable quantities of inhibitor I. Inhibitor I synthesis in tobacco crown gall tumors paralleled tumor growth at the average rate of about 4.5 μg of inhibitor I per 200 mg of fresh tissue per day. Infection of variegated tobacco mutant Dp-I with A. tumefaciens strain CG-14 produced tumors with 25% more inhibitor than tumors induced with strain B6. Unlike tobacco, tumors induced by either bacterial strain on potato (Solanum tuberosum) and on tomato (Lycopersicum esculentum) did not accumulate inhibitor I. Consequently, inhibitor I accumulation is modulated by the type of plant host used in spite of familial relatedness (Solanaceae) and the strain of A. tumefaciens used for infection. 相似文献
103.
Coactivator binding promotes the specific interaction between ligand and the pregnane X receptor 总被引:8,自引:0,他引:8
The pregnane X receptor (PXR) detects the presence of a wide variety of endogenous and xenobiotic compounds, and is a master regulator of the expression of genes central to drug metabolism and excretion. We present the 2.0A crystal structure of the human PXR ligand-binding domain (LBD) in complex with the cholesterol-lowering compound SR12813 and a 25 amino acid residue fragment of the human steroid receptor coactivator-1 (SRC-1) containing one LXXLL motif. PXR crystallizes as a homodimer in the asymmetric unit in this structure and possesses a novel alpha2 helix adjacent to its ligand-binding cavity. The SRC-1 peptide forms two distinct helices and binds adjacent to the ligand-dependent transactivation AF-2 helix on the surface of PXR. In contrast with previous PXR structures, in which SR12813 bound in multiple orientations, the small SR12813 agonist in this structure binds in a single, unique orientation within the receptor's ligand-binding pocket and contacts the AF-2 helix. Thermal denaturation studies reveal that the SR12813 ligand and SRC-1 coactivator peptide each stabilize the LBD of PXR, and that together they exert an additive effect on the stability of the receptor. These results indicate that the binding of coactivator to the surface of PXR limits the ability of this promiscuous receptor to "breathe" and helps to trap a single, active conformation of SR12813. They further reveal that specificity is required for PXR activation. 相似文献
104.
Fisher MJ Backer RT Husain S Hsiung HM Mullaney JT O'Brian TP Ornstein PL Rothhaar RR Zgombick JM Briner K 《Bioorganic & medicinal chemistry letters》2005,15(20):4459-4462
Substitution of the aryl sulfonamide moiety contained in MC4 agonist 1 with bicyclic heterocycles and aminotetralines produced compounds with MC4 activity. The heterocycles represent alternative privileged structures to that contained in 1. Compounds in which the polar group of the privileged structure was displayed in an endocyclic fashion were not as active as the parent agonist 1, while those with an exocyclic polar group afforded activity competitive with 1. 相似文献
105.
A set of proteins and noncoding RNAs,referred to as the male specific lethal (MSL) complex,is present on the male X chromosome in Drosophila and has been postulated to be responsible for dosage compensation of this chromosome - the up-regulation of its expression to be equal to that of two X chromosomes in females.This hypothesis is evaluated in view of lesser known aspects of dosage compensation such as the fact that metafemales with three X chromosomes also have equal expression to normal females,which would require a down-regulation of each gene copy.Moreover,when this complex is ectopically expressed in females or specifically targeted to a reporter in males,there is no increase in expression of the genes or targets with which it is associated.These observations are not consistent with the hypothesis that the MSL complex conditions dosage compensation.A synthesis is described that can account for these observations. 相似文献
106.
Chartier-Harlin MC Dachsel JC Vilariño-Güell C Lincoln SJ Leprêtre F Hulihan MM Kachergus J Milnerwood AJ Tapia L Song MS Le Rhun E Mutez E Larvor L Duflot A Vanbesien-Mailliot C Kreisler A Ross OA Nishioka K Soto-Ortolaza AI Cobb SA Melrose HL Behrouz B Keeling BH Bacon JA Hentati E Williams L Yanagiya A Sonenberg N Lockhart PJ Zubair AC Uitti RJ Aasly JO Krygowska-Wajs A Opala G Wszolek ZK Frigerio R Maraganore DM Gosal D Lynch T Hutchinson M Bentivoglio AR Valente EM Nichols WC Pankratz N 《American journal of human genetics》2011,(3):140-406
Genome-wide analysis of a multi-incident family with autosomal-dominant parkinsonism has implicated a locus on chromosomal region 3q26-q28. Linkage and disease segregation is explained by a missense mutation c.3614G>A (p.Arg1205His) in eukaryotic translation initiation factor 4-gamma (EIF4G1). Subsequent sequence and genotype analysis identified EIF4G1 c.1505C>T (p.Ala502Val), c.2056G>T (p.Gly686Cys), c.3490A>C (p.Ser1164Arg), c.3589C>T (p.Arg1197Trp) and c.3614G>A (p.Arg1205His) substitutions in affected subjects with familial parkinsonism and idiopathic Lewy body disease but not in control subjects. Despite different countries of origin, persons with EIF4G1 c.1505C>T (p.Ala502Val) or c.3614G>A (p.Arg1205His) mutations appear to share haplotypes consistent with ancestral founders. eIF4G1 p.Ala502Val and p.Arg1205His disrupt eIF4E or eIF3e binding, although the wild-type protein does not, and render mutant cells more vulnerable to reactive oxidative species. EIF4G1 mutations implicate mRNA translation initiation in familial parkinsonism and highlight a convergent pathway for monogenic, toxin and perhaps virally-induced Parkinson disease. 相似文献
107.
Ontogenetic changes in the human femur associated with the acquisition of bipedal locomotion, especially the development of the bicondylar angle, have been well documented. The purpose of this study is to quantify changes in the three-dimensional structure of trabecular bone in the human proximal femur in relation to changing functional and external loading patterns with age. High-resolution X-ray computed tomography scan data were collected for 15 juvenile femoral specimens ranging in age from prenatal to approximately nine years of age. Serial slices were collected for the entire proximal femur of each individual with voxel resolutions ranging from 0.017 to 0.046 mm depending on the size of the specimen. Spherical volumes of interest were defined within the proximal femur, and the bone volume fraction, trabecular thickness, trabecular number, and fabric anisotropy were calculated in three dimensions. Bone volume fraction, trabecular number, and degree of anisotropy decrease between the age of 6 months and 12 months, with the lowest values for these parameters occurring in individuals near 12 months of age. By age 2-3 years, the bone volume, thickness, and degree of anisotropy increase slightly, and regions in the femoral neck become more anisotropic corresponding to the thickening of the inferior cortical bone of the neck. These results suggest that trabecular structure in the proximal femur reflects the shift in external loading patterns associated with the initiation of unassisted walking in infants. 相似文献
108.
109.
110.
Purification of Potato Leaf Plasma Membrane Protein pp34, a Protein Phosphorylated in Response to Oligogalacturonide Signals for Defense and Development 总被引:3,自引:0,他引:3 下载免费PDF全文
A potato (Solanum tuberosum L.) plasma membrane protein called pp34, the only known example of a plasma membrane protein that is phosphorylated specifically in response to defined Oligogalacturonide signals in plants, has been purified to apparent homogeneity. Polyclonal antibodies raised in rabbits against the purified pp34 protein immunoprecipitated a single thiophosphorylated protein species from potato plasma membranes, as analyzed by two-dimensional denaturing electrophoresis and fluorography. The pp34 antibodies also recognized a single protein in tomato (Lycopersicon esculentum L.) membranes that is thiophosphorylated in response to Oligogalacturonide elicitors, as demonstrated by western blotting and specific immunoprecipitation. These experiments confirm the identity of the tomato membrane protein as a pp34 homolog and establish the high monospecificity of the pp34 antibodies. This will permit further investigation of the role of protein phosphorylation in oligouronide signaling for defensive genes in potato and tomato plants. 相似文献