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81.
Cantu C Benlagha K Savage PB Bendelac A Teyton L 《Journal of immunology (Baltimore, Md. : 1950)》2003,170(9):4673-4682
CD1 resembles both class I and class II MHC but differs by the important aspect of presenting lipid/glycolipids, instead of peptides, to T cells. Biophysical studies of lipid/CD1 interactions have been limited, and kinetics of binding are in contradiction with functional studies. We have revisited this issue by designing new assays to examine the loading of CD1 with lipids. As expected for hydrophobic interactions, binding affinity was not high and had limited specificity. Lipid critical micelle concentration set the limitation to these studies. Once loaded onto CD1d, the recognition of glycolipids by alphabeta T cell receptor was studied by surface plasmon resonance using soluble Valpha14-Vbeta8.2 T cell receptors. The Valpha14 Jalpha18 chain could be paired with NK1.1 cell-derived Vbeta chain, or any Vbeta8 chain, to achieve high affinity recognition of alpha-galactosylceramide. Biophysical analysis indicated little effect of temperature or ionic strength on the binding interaction, in contrast to what has been seen in peptide/MHC-TCR studies. This suggests that there is less accommodation made by this TCR in recognizing alpha-galactosylceramide, and it can be assumed that the most rigid part of the Ag, the sugar moiety, is critical in the interaction. 相似文献
82.
Kery V Savage JR Widjaja K Blake BK Conklin DR Ho YS Long X von Rechenberg M Zarembinski TI Boniface JJ 《Analytical biochemistry》2003,317(2):255-258
High-throughput purification of affinity-tagged fusion proteins is currently one of the fastest developing areas of molecular proteomics. A prerequisite for success in protein purification is sufficient soluble protein expression of the target protein in a heterologous host. Hence, a fast and quantitative evaluation of the soluble-protein levels in an expression system is one of the key steps in the entire process. Here we describe a high-throughput expression screen for affinity-tagged fusion proteins based on an enzyme linked immunofiltration assay (ELIFA). An aliquot of a crude Escherichia coli extract containing the analyte, an affinity-tagged protein, is adsorbed onto the membrane. Subsequent binding of specific antibodies followed by binding of a secondary antibody horseradish peroxidase (HRP) complex then allows quantitative evaluation of the analyte using tetramethylbenzidine as the substrate for HRP. The method is accurate and quantitative, as shown by comparison with results from western blotting and an enzymatic glutathione S-transferase (GST) assay. Furthermore, it is a far more rapid assay and less cumbersome than western blotting, lending itself more readily to high-throughput analysis. It can be used at the expression level (cell lysates) or during the subsequent purification steps to monitor yield of specific protein. 相似文献
83.
84.
Liu H Radhakrishnan P Magoun L Prabu M Campellone KG Savage P He F Schiffer CA Leong JM 《Molecular microbiology》2002,45(6):1557-1573
Attachment to host cells by enterohaemorrhagic Escherichia coli (EHEC) is associated with the formation of a highly organized cytoskeletal structure containing filamentous actin, termed an attaching and effacing (AE) lesion. Intimin, an outer membrane protein of EHEC, is required for the formation of AE lesions, as is Tir, a bacterial protein that is translocated into the host cell to function as a receptor for intimin. We established a yeast two-hybrid assay for intimin-Tir interaction and, after random mutagenesis, isolated 24 point mutants in intimin, which disrupted Tir recognition in this system. Analysis of 11 point mutants revealed a correlation between recognition of recombinant Tir and the ability to trigger AE lesions. Many of the mutations fell within a 50-residue region near the C-terminus of intimin. Alanine-scanning mutagenesis of this region revealed four residues (Ser890, Thr909, Asn916 and Asn927) that are critical for Tir recognition. Mapping the sequences of EHEC intimin and Tir onto the crystal structure of the intimin-Tir complex of enteropathogenic E. coli predicts that each of these four intimin residues lies at the intimin-Tir interface and contributes to a pocket that interacts with Ile298 of EHEC Tir. Thus, this genetic approach to intimin function both identified residues critical for Tir binding and demonstrated a correlation between the ability to bind Tir and the ability to trigger actin focusing. 相似文献
85.
Savage MO Scommegna S Carroll PV Ho JT Monson JP Besser GM Grossman AB 《Hormone research》2002,58(Z1):39-43
Growth is disturbed by adrenal hypersecretion of androgens or cortisol. Androgen excess in virilizing adrenal tumours causes advanced growth and bone age. In 9 girls with virilizing tumours, mean heights at diagnosis and final heights were 1.23 +/- 0.42 and 1.3 +/- 0.37 SDS respectively. In poorly controlled CAH, excess androgens cause early epiphyseal fusion and adult short stature. Increased growth occurs only after 18 months of age, even in untreated CAH, i.e. hydrocortisone >10 mg/m(2)/day is not generally required and may suppress infantile growth, affecting childhood and adult height. Growth was studied in 19 patients, aged 6.4-17.8 years, with Cushing's disease (CD). At diagnosis, mean height SDS was -1.81 (1.2 to -4.17), 53% < -1.8 SDS, height velocity in 6 was 0.9-3.8 cm/year and mean BMI SDS 2.29 (0.7-5.06). From 1983 to 2001, CD was cured in 18 patients (61%) by transsphenoidal surgery (TSS) alone and 39% by TSS plus pituitary irradiation (RT). In 13 patients, growth hormone (GH) was assessed by ITT/glucagons at 1-108 months after cure. Four had severe GH deficiency (<9 mU/l), 7 subnormal (10-29 mU/l) and 2 normal (>30 mU/l) GH status. Subnormal GH was present in 7 subjects >2 years after TSS or RT cure. In 10 subjects, aged 12.9 +/- 3.4 years, growth after cure was studied for 9.1 +/- 5.0 years. Nine had no catch-up growth in the interval of 0.3-1.1 years after cure (mean HV 5.3 +/- 2.4 cm/year). All these had GH deficiency peak GH 0.5-20.9 mU/l, and received hGH 2.7 mg/m(2)/week, 3 with GnRHa. All 10 showed long-term catch-up growth with mean delta SDS at diagnosis (Ht SDS-target Ht SDS) -1.72 +/- 1.26 improving to -0.83 +/- 1.08 (p = 0.0005) at latest of final Ht. At diagnosis, virilization was present in 82% of 17 patients with CD. Mean SDS values of serum androstenedione, DHEA-S and testosterone were normal, i.e. 0.72 (-2.9 to 3.0), -0.8 (6.0 to 2.2), 0.7 (-7.9 to 9.5) respectively, whereas SHBG was reduced at -2.1 (-5.3 to 1.2), increasing free androgen levels. Bone age (BA) was delayed (mean 1.46 years) in 14/16 patients, suggesting cortisol excess contributed more then androgen effect to skeletal maturation. In conclusion, most paediatric patients with CD had subnormal linear growth with delayed BA. After cure by TSS or pituitary irradiation, GH deficiency was frequent and persisted for many years. Treatment with hGH induced significant long-term catch-up growth leading to reasonable final height. 相似文献
86.
Seligman LM Chisholm KM Chevalier BS Chadsey MS Edwards ST Savage JH Veillet AL 《Nucleic acids research》2002,30(17):3870-3879
The homing endonuclease I-CreI recognizes and cleaves a particular 22 bp DNA sequence. The crystal structure of I-CreI bound to homing site DNA has previously been determined, leading to a number of predictions about specific protein–DNA contacts. We test these predictions by analyzing a set of endonuclease mutants and a complementary set of homing site mutants. We find evidence that all structurally predicted I-CreI/DNA contacts contribute to DNA recognition and show that these contacts differ greatly in terms of their relative importance. We also describe the isolation of a collection of altered specificity I-CreI derivatives. The in vitro DNA-binding and cleavage properties of two such endonucleases demonstrate that our genetic approach is effective in identifying homing endonucleases that recognize and cleave novel target sequences. 相似文献
87.
Tuohy MG Walsh DJ Murray PG Claeyssens M Cuffe MM Savage AV Coughlan MP 《Biochimica et biophysica acta》2002,1596(2):366-380
Three forms of cellobiohydrolase (EC 3.2.1.91), CBH IA, CBH IB and CBH II, were isolated to apparent homogeneity from culture filtrates of the aerobic fungus Talaromyces emersonii. The three enzymes are single sub-unit glycoproteins, and unlike most other fungal cellobiohydrolases are characterised by noteworthy thermostability. The kinetic properties and mode of action of each enzyme against polymeric and small soluble oligomeric substrates were investigated in detail. CBH IA, CBH IB and CBH II catalyse the hydrolysis of microcrystalline cellulose, albeit to varying extents. Hydrolysis of a soluble cellulose derivative (CMC) and barley 1,3;1,4-beta-D-glucan was not observed. Cellobiose (G2) is the main reaction product released by CBH IA, CBH IB, and CBH II from microcrystalline cellulose. All three CBHs are competitively inhibited by G2; inhibition constant values (K(i)) of 2.5 and 0.18 mM were obtained for CBH IA and CBH IB, respectively (4-nitrophenyl-beta-cellobioside as substrate), while a K(i) of 0.16 mM was determined for CBH II (2-chloro-4-nitrophenyl-beta-cellotrioside as substrate). Bond cleavage patterns were determined for each CBH on 4-methylumbelliferyl derivatives of beta-cellobioside and beta-cellotrioside (MeUmbG(n)). While the Tal. emersonii CBHs share certain properties with their counterparts from Trichoderma reesei, Humicola insolens and other fungal sources, distinct differences were noted. 相似文献
88.
Beisson F Koo AJ Ruuska S Schwender J Pollard M Thelen JJ Paddock T Salas JJ Savage L Milcamps A Mhaske VB Cho Y Ohlrogge JB 《Plant physiology》2003,132(2):681-697
The genome of Arabidopsis has been searched for sequences of genes involved in acyl lipid metabolism. Over 600 encoded proteins have been identified, cataloged, and classified according to predicted function, subcellular location, and alternative splicing. At least one-third of these proteins were previously annotated as "unknown function" or with functions unrelated to acyl lipid metabolism; therefore, this study has improved the annotation of over 200 genes. In particular, annotation of the lipolytic enzyme group (at least 110 members total) has been improved by the critical examination of the biochemical literature and the sequences of the numerous proteins annotated as "lipases." In addition, expressed sequence tag (EST) data have been surveyed, and more than 3,700 ESTs associated with the genes were cataloged. Statistical analysis of the number of ESTs associated with specific cDNA libraries has allowed calculation of probabilities of differential expression between different organs. More than 130 genes have been identified with a statistical probability > 0.95 of preferential expression in seed, leaf, root, or flower. All the data are available as a Web-based database, the Arabidopsis Lipid Gene database (http://www.plantbiology.msu.edu/lipids/genesurvey/index.htm). The combination of the data of the Lipid Gene Catalog and the EST analysis can be used to gain insights into differential expression of gene family members and sets of pathway-specific genes, which in turn will guide studies to understand specific functions of individual genes. 相似文献
89.
The paper extends previous research published by Cohen, Machalek, Vila, and others on the evolutionary-ecological paradigm for understanding criminal behavior. After reviewing literature related to human ecology and crime, the paper focuses on elements relevant to human ecology-biology, development, and ecological factors--and their role in criminal behavior. Major emphasis is placed on the linkages between individual factors and macro-level crime using chronic offending as a case in point. The principles of evolutionary ecology then are used to discuss counterstrategies to crime, and the prospects for protection/avoidance, deterrent, and nurturant strategies in light of evidence on chronic offending. 相似文献
90.
Two Dictyostelium orthologs of the prokaryotic cell division protein FtsZ localize to mitochondria and are required for the maintenance of normal mitochondrial morphology
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Gilson PR Yu XC Hereld D Barth C Savage A Kiefel BR Lay S Fisher PR Margolin W Beech PL 《Eukaryotic cell》2003,2(6):1315-1326
In bacteria, the protein FtsZ is the principal component of a ring that constricts the cell at division. Though all mitochondria probably arose through a single, ancient bacterial endosymbiosis, the mitochondria of only certain protists appear to have retained FtsZ, and the protein is absent from the mitochondria of fungi, animals, and higher plants. We have investigated the role that FtsZ plays in mitochondrial division in the genetically tractable protist Dictyostelium discoideum, which has two nuclearly encoded FtsZs, FszA and FszB, that are targeted to the inside of mitochondria. In most wild-type amoebae, the mitochondria are spherical or rod-shaped, but in fsz-null mutants they become elongated into tubules, indicating that a decrease in mitochondrial division has occurred. In support of this role in organelle division, antibodies to FszA and FszA-green fluorescent protein (GFP) show belts and puncta at multiple places along the mitochondria, which may define future or recent sites of division. FszB-GFP, in contrast, locates to an electron-dense, submitochondrial body usually located at one end of the organelle, but how it functions during division is unclear. This is the first demonstration of two differentially localized FtsZs within the one organelle, and it points to a divergence in the roles of these two proteins. 相似文献