Substitutions for Glu-537 of beta-galactosidase from Escherichia coli cause large decreases in catalytic activity

Glu-537 of beta-galactosidase (EC 3.2.1.23) was replaced by Asp, Gln and Val using synthetic oligonucleotides. The kcat values of the purified enzyme mixtures were reduced by about 100-fold for the Asp mutant, 30,000-60,000-fold for the Val mutant and 160,000-300,000-fold for the Gln mutant. The greatest differences in properties from the wild-type enzyme were found for the Asp-substituted enzyme: the Km values increased (from 0.12 to 0.42 mM for o-nitrophenyl beta-D-galactopyranoside), and from 0.04 to 0.37 mM for p-nitrophenyl beta-D-galactopyranoside), the Ki value for isopropyl beta-D-galactopyranoside increased (from 0.11 to 0.30 mM), the stability to heat decreased and methanol did not act as an acceptor. The enzymes with the other two substitutions had properties similar to those of the wild-type. For all three substituted enzymes, the inhibitory effects of the transition-state analogues (2-deoxy-2-amino-D-galactose and L-ribose) and the Mg2+ effects were similar to those of the normal enzyme. As all of the properties (except the kcat values) of the Gln- and Val-substituted enzyme preparations were similar to those of the wild-type enzyme, the activities in those preparations were probably due to the presence of a few wild-type enzyme molecules (formed from misreads) among the substituted enzymes. The enzymes with Gln and Val substitutions appear to be totally inactive. The results obtained support a recent suggestion that Glu-537 is an important catalytic residue of beta-galactosidase.

Multi-target PCR analysis by capillary electrophoresis and laser-induced fluorescence

Quantitative analysis of polymerase chain reaction (PCR) amplified HIV-1 DNA or cDNA fragments is attained using an automated system that combines capillary-gel electrophoresis (CGE) for high-efficiency separation and laser-induced fluorescence (LIF) for high-sensitivity detection. This system enables the detection of PCR-amplified multiple target DNA or cDNA in the same tube by a single injection with high precision.

The signalling pathways of interleukin-6 and gamma interferon converge by the activation of different transcription factors which bind to common responsive DNA elements

Interleukin-6 (IL-6) and gamma interferon (IFN-gamma) induce a partially overlapping set of genes, including the genes for interferon regulatory factor 1 (IRF-1), intercellular adhesion molecule 1 (ICAM-1), and the acute-phase protein alpha 2-macroglobulin. We report here that the rat alpha 2-macroglobulin promoter is activated by IFN-gamma in human hepatoma (HepG2) cells and that the IFN-gamma response element maps to the same site previously defined as the acute-phase response element (APRE), which binds the IL-6-activated transcription factor APRF (acute-phase response factor). As was reported for fibroblasts, the IFN-gamma-regulated transcription factor GAF is phosphorylated at tyrosine after IFN-gamma treatment of HepG2 cells. IFN-gamma posttranslationally activates a protein which specifically binds to the alpha 2-macroglobulin APRE. This protein is shown to be identical or closely related to GAF. Although APRF and GAF are shown to represent different proteins, their binding sequence specificities are very similar. APRF and GAF bind equally well to the APRE sequences of various acute-phase protein genes as well as to the IFN-gamma response elements of the IRF-1, ICAM-1, and other IFN-gamma-inducible genes. Transient transfection analysis revealed that the IFN-gamma response elements of the IRF-1 and ICAM-1 promoters are able to confer responsiveness to both IFN-gamma and IL-6 onto a heterologous promoter. Therefore, APRF and GAF are likely to be involved in the transcriptional induction of these immediate-early genes by IL-6 and IFN-gamma, respectively. Taken together, these results demonstrate that two functionally distinct hormones, IL-6 and IFN-gamma, act through common regulatory elements to which different transcription factors sharing almost the same sequence specificity bind.

Prevention of vertebrate neuronal death by the crmA gene

Interleukin-1 beta converting enzyme (ICE) is a mammalian homolog of CED-3, a protein required for programmed cell death in the nematode Caenorhabditis elegans. The activity of ICE can be specifically inhibited by the product of crmA, a cytokine response modifier gene encoded by cowpox virus. Microinjection of the crmA gene into chicken dorsal root ganglion neurons was found to prevent cell death induced by deprivation of nerve growth factor. Thus, ICE is likely to participate in neuronal death in vertebrates.

Association of transcription factor APRF and protein kinase Jak1 with the interleukin-6 signal transducer gp130

Interleukin-6 (IL-6), leukemia inhibitory factor, oncostatin M, interleukin-11, and ciliary neurotrophic factor bind to receptor complexes that share the signal transducer gp130. Upon binding, the ligands rapidly activate DNA binding of acute-phase response factor (APRF), a protein antigenically related to the p91 subunit of the interferon-stimulated gene factor-3 alpha (ISGF-3 alpha). These cytokines caused tyrosine phosphorylation of APRF and ISGF-3 alpha p91. Protein kinases of the Jak family were also rapidly tyrosine phosphorylated, and both APRF and Jak1 associated with gp130. These data indicate that Jak family protein kinases may participate in IL-6 signaling and that APRF may be activated in a complex with gp130.

Model-based quality control of the baker's yeast Saccharomyces cerevisiae

This paper deals with the optimal control of storage stability for compressed baker's yeast by minimizing the fraction of budding cells (FBC) based on a metabolic and cell cyclic model system for Saccharomyces cerevisiae. Three experiments of quality control were successfully carried out. The experimental data revealed that under optimal operation conditions, the final FBC-values approached the theoretical minimum and that storage stability was enhanced.

Codeine toxicokinetics in rats during a two-year dosed feed study

Codeine toxicokinetics in F344 rats of both sexes were determined during a 2-year chronic toxicology study using dosed feed as the exposure route with a 12-hr light/dark cycle starting at 7:00 a.m. Rats were allowed to access to dosed feed formulations ad libitum with codeine concentrations at 0, 400, 800, and 1600 ppm. Blood samples were collected from individual rat on days 7, 21, and 90 at 7:00 p.m., 11:00 p.m., 3:00 a.m., and 7:00 a.m. Additional samples were collected at 16 and 24 months between 6:00-8:00 a.m. Plasma concentrations of codeine and morphine were determined directly by radioimmunoassay. Concentrations of their conjugates were determined indirectly by measuring the total amount of free codeine and morphine released after samples were treated with beta-glucuronidase. Results indicated that plasma concentrations of both codeine and morphine steadily decreased from day 7 to 16 months and then rebounded at 24 months. Results also indicated that plasma concentrations of both codeine and morphine correlated well with the amounts of codeine added to the feed. Bioavailability of codeine using the dosed feed route increased with dose, varying from 10% to 25%, which was somewhat higher than the previously reported approximately 8% bioavailability using the gavage route. Concentrations of conjugated codeine were very low, whereas concentrations of conjugated morphine were very high. These results suggested that demethylation of codeine to morphine in rats is the main metabolic pathway and was maintained over the course of the study.

An efficient method for large-scale isolation of plasmid DNAs by heat-alkali co-denaturation

A method is presented for efficient and large-scale isolation of plasmid DNAs from bacterial cells. Based on the cooperativity of heat and alkali actions, the method provides DNA preparations with high quality and yield (about 2 micrograms of DNA/ml culture), which are completely digestable by restriction enzymes and have a high transformation efficiency. Furthermore, the DNA preparations are extremely stable, and even through 4-year storage at -20 degrees C, the electrophorogram and transformation efficiency remain as high as before. The factors affecting the stability of various DNA samples are discussed.

Purification and properties of a glycerophosphocholine phosphodiesterase from bovine brain myelin

An enzyme releasing phosphocholine from glycerophosphocholine was purified to apparent homogeneity based upon SDS-PAGE. The enzyme was liberated from lyophilized bovine myelin by differential detergent extraction and final purification was accomplished with Q-Sepharose Fast Flow chromatography yielding an apparently homogeneous protein. The molecular mass based upon PAGE was approximately 14 kDa. The enzyme was also capable of releasing p-nitrophenol from p-nitrophenyl-phosphocholine. Maximal activity was obtained with 0.2 mM ZnCl2 or 1 mM CoCl2. p-Nitrophenylphosphocholine and phosphocholine were competitive inhibitors of glycerophosphocholine hydrolysis with Ki's of 0.028 mM and 0.03 mM respectively. Glycerophosphocholine and phosphocholine were competitive inhibitors of p-nitrophenylphosphocholine hydrolysis with Ki's of 0.5 mM and 1.75 mM respectively.

Induction of apoptosis in fibroblasts by IL-1 beta-converting enzyme, a mammalian homolog of the C. elegans cell death gene ced-3

The mammalian interleukin-1 beta-converting enzyme (ICE) has sequence similarity to the C. elegans cell death gene ced-3. We show here that overexpression of the murine ICE (mICE) gene or of the C. elegans ced-3 gene causes Rat-1 cells to undergo programmed cell death. Point mutations in a region homologous between mICE and CED-3 eliminate the ability of mICE and ced-3 to cause cell death. The cell death caused by mICE can be suppressed by overexpression of the crmA gene, a specific inhibitor of ICE, as well as by bcl-2, a mammalian oncogene that can act to prevent programmed cell death. Our results suggest that ICE may function during mammalian development to cause programmed cell death.

The C. elegans cell death gene ced-3 encodes a protein similar to mammalian interleukin-1 beta-converting enzyme

We have cloned the C. elegans cell death gene ced-3. A ced-3 transcript is most abundant during embryogenesis, the stage during which most programmed cell deaths occur. The predicted CED-3 protein shows similarity to human and murine interleukin-1 beta-converting enzyme and to the product of the mouse nedd-2 gene, which is expressed in the embryonic brain. The sequences of 12 ced-3 mutations as well as the sequences of ced-3 genes from two related nematode species identify sites of potential functional importance. We propose that the CED-3 protein acts as a cysteine protease in the initiation of programmed cell death in C. elegans and that cysteine proteases also function in programmed cell death in mammals.

Nonrandom association of free iron with membranes of sickle and beta-thalassemic erythrocytes

To further define the nature of abnormal iron deposits on the membranes of pathologic red blood cells, we have used sickle cell anemia (HbSS), HbSC, and beta-thalassemic erythrocytes (RBCs) to prepare inside-out membranes (IOM) and insoluble membrane aggregates (AGGs) containing coclustered hemichrome and band 3. Study of IOM from HbSC and thalassemic patients showed that amounts of heme iron and, especially, free iron were much higher in patients who had undergone surgical splenectomy. The membrane AGGs from HbSS and beta-thalassemic RBCs contained much more globin than heme, with this discrepancy being variable from patient to patient. Although these AGGs were enriched (compared with the ghosts from which they were derived) for heme, as expected, less than 10% of total ghost heme was recovered in them. Remarkably, these AGGs also were enriched for nonheme iron, markedly so in some patients. Iron binding studies showed that the association of free iron with these hemichrome/band 3 AGGs is explained by the fact that free iron binds to denatured hemoglobin. These results document that free iron is nonrandomly associated with the membranes of sickle and beta-thalassemic RBCs. Whether this plays a causative role in the premature removal of such cells from the circulation remains to be seen.

Multiple pathways for protein transport into or across the thylakoid membrane

Many thylakoid proteins are cytosolically synthesized and have to cross the two chloroplast envelope membranes as well as the thylakoid membrane en route to their functional locations. In order to investigate the localization pathways of these proteins, we over-expressed precursor proteins in Escherichia coli and used them in competition studies. Competition was conducted for import into the chloroplast and for transport into or across isolated thylakoids. We also developed a novel in organello method whereby competition for thylakoid transport occurred within intact chloroplasts. Import of all precursors into chloroplasts was similarly inhibited by saturating concentrations of the precursor to the OE23 protein. In contrast, competition for thylakoid transport revealed three distinct precursor specificity groups. Lumen-resident proteins OE23 and OE17 constitute one group, lumenal proteins plastocyanin and OE33 a second, and the membrane protein LHCP a third. The specificity determined by competition correlates with previously determined protein-specific energy requirements for thylakoid transport. Taken together, these results suggest that thylakoid precursor proteins are imported into chloroplasts on a common import apparatus, whereupon they enter one of several precursor-specific thylakoid transport pathways.

Glycerophosphorylcholine phosphocholine phosphodiesterase activity during the differentiation of glial progenitor cells

O-2A progenitor cells were grown in medium containing either 1% or 10% fetal calf serum (FCS) for 4 weeks. The cells in 1% FCS were 75% oligodendrocytes by 3 weeks in culture. The cell population was so overgrown with astrocytes in the 10% medium that an accurate estimate of cell number could not be made. The activities of glycerophosphorylcholine phosphocholine phosphodiesterase (GPC-PC-PdE), p-nitrophenylphosphorylcholine phosphodiesterase (pNPPC-PC-PdE), and ceramide UDP galactose galactosyl transferase (CGalT) were barely detectable in the cells grown in 10% FCS. The activities of these 3 enzymes were low in the cells grown in 1% FCS for the first 2 weeks and then all 3 increased manyfold. These observations reinforce the evidence previously accrued showing that these two phosphodiesterase activities (GPC-PC-PdE and pNPPC-PC-PdE) are markers of oligodendroglial cells as well as myelin. In contrast, glycerophosphorylcholine choline phosphodiesterase (GPC-C-PdE) activities were present in cells grown in both 1% and 10% FCS.

Determination of apolipoprotein E genotypes by single-strand conformational polymorphism

We used single-strand conformational polymorphism (SSCP) to determine apolipoprotein E (Apo E) genotypes in 47 individuals. A 295-base-pair (bp) DNA fragment coding for amino acid residues 80-178 of the Apo E protein gave distinct patterns for the three alleles. When we used SSCP to determine the Apo E polymorphism of five individuals whose phenotyping results differed from those of genotyping, the SSCP results agreed with the genotyping results obtained by the PCR-based amplification refractory mutation system (ARMS). Because most of the reported rare alleles of the Apo E gene involve mutations of amino acid residues in positions 120-160, our SSCP method is useful for determining rare as well as common alleles.

Determination of apolipoprotein E genotypes by single-strand conformational polymorphism

We used single-strand conformational polymorphism (SSCP) to determine apolipoprotein E (Apo E) genotypes in 47 individuals. A 295-base-pair (bp) DNA fragment coding for amino acid residues 80-178 of the Apo E protein gave distinct patterns for the three alleles. When we used SSCP to determine the Apo E polymorphism of five individuals whose phenotyping results differed from those of genotyping, the SSCP results agreed with the genotyping results obtained by the PCR-based amplification refractory mutation system (ARMS). Because most of the reported rare alleles of the Apo E gene involve mutations of amino acid residues in positions 120-160, our SSCP method is useful for determining rare as well as common alleles.

Stromal factor plays an essential role in protein integration into thylakoids that cannot be replaced by unfolding or by heat shock protein Hsp70

The light-harvesting chlorophyll a/b protein (LHCP) is an integral thylakoid membrane protein. It is made in the cytosol as a precursor (pLHCP), imported into chloroplasts, and subsequently integrated into thylakoids. Integration of pLHCP into thylakoids requires a stromal protein factor that functions in part to maintain the solubility and integration competence of pLHCP. Recently, it was reported that unfolded pLHCP was sufficient for integration and that the stromal factor, identified as the plastid Hsp70, was required only to prevent pLHCP refolding [Yalovsky, S., Paulsen, H., Michaeli, D., Chitnis, P. R. & Nechushtai, R. (1992) Proc. Natl. Acad. Sci. USA 89, 5616-5619]. Our studies, using more rigorous criteria for integration, show that unfolded pLHCP is not sufficient; stromal factor is an absolute requirement for integration. Furthermore, experiments with purified Hsp70 as well as Hsp70-depleted stromal extract demonstrate that Hsp70 is not the stromal factor. These results plus the finding that pLHCP diluted out of urea is relatively stable as a substrate for integration point to an additional role for the stromal factor in targeting and/or membrane translocation.

Accelerated programmed cell death (apoptosis) in erythroid precursors of patients with severe beta-thalassemia (Cooley's anemia)

The profound and life-threatening anemia in patients with Cooley's anemia is ascribed primarily to intramedullary hemolysis (ineffective erythropoiesis), the cause of which is obscure. Based on prior morphologic data showing nuclear abnormalities, we hypothesized that accelerated apoptosis could occur in these erythroid precursors. The highly successful bone marrow (BM) transplantation program for patients with Cooley's anemia provided us with a unique opportunity to test this hypothesis. We obtained pretransplantation BM aspiration samples from patients undergoing BM transplantation in Pesaro, Italy and from their allogeneic donors. The erythroid precursors were isolated using ficoll sedimentation and then panning selecting fro CD45- cells. Cytospin and Giemsa staining showed that the separation provided greater than 90% erythroblasts. Five million of these erythroblasts were lysed and their DNA was isolated. There were obvious ladder patterns of DNA breakdown products in beta-thalassemia major samples, with less occurring in beta-thalassemia trait. Normal individuals showed only a slight smear of breakdown of DNA. These results indicate there is enhanced apoptosis in the erythroblasts in the BMs of Cooley's anemia patients. This finding might partially explain why most of these erythroblasts never survive to become mature erythrocytes.

Characterization of the autologous antibodies that opsonize erythrocytes with clustered integral membrane proteins

In earlier studies we presented evidence that the clustering of the integral membrane protein, band 3, can serve as a signal for immune recognition and clearance of senescent or abnormal erythrocytes from circulation. In this study, we have exploited the capacity of 1 mmol/L Zn+2 to mildly and reversibly cluster band 3 in situ to characterize the nature of the autologous antibodies specific for the clustered state. We report that the autologous IgG elute almost exclusively in a high molecular weight complex with other proteins when C12E8 detergent extracts of Zn clustered membranes are chromatographed on Sepharose CL-6B. The complex was also seen to contain complement component C3, hemoglobin, and a cross-linked oligomer of band 3. Autologous IgG and complement were virtually absent from all other fractions. When the band 3 clusters were disaggregated by removal of the Zn+2, the autologous IgG eluted from the erythrocyte surface. Collection of this IgG and use of the antibody in immunoblots of erythrocyte membranes showed that the band 3 monomer, dimer, and oligomers were the major antigenic species. Except for a minor unidentified band at approximately 78,000 d, no other proteins were significantly stained. Curiously, band 3 showed an uneven staining pattern, with oligomers and the leading edge of the monomers appearing more intensely than expected from their abundances in the Coomassie blue-stained gels. Typing of the same autologous IgG with monoclonal antibodies specific for the different subclasses of IgG showed the presence of only subtypes 2 and 3. Taken together, these data suggest that a specific population of autologous IgG recognizes sites of integral membrane protein clustering (a common lesion in senescent and abnormal red blood cells) and that the antigen within these clusters involves an aggregated state of band 3.

Schistosomiasis japonica on Jishan Island, Jiangxi Province, People's Republic of China: persistence of hepatic fibrosis after reduction of the prevalence of infection with age

Hepatic fibrosis due to schistosomiasis japonica was examined by ultrasonography in a cross-sectional community study of 825 individuals on Jishan Island, Jiangxi Province, China. The prevalence of active infection was 39.4% with peak infection in the 10-19.9 years age group followed by a significant decline. A similar pattern was observed for intensity of infection. The prevalence of hepatomegaly in the midsternal line > or = 6 cm peaked at 60% in the fourth decade and remained elevated. A progressive increase in the severity of hepatic periportal fibrosis was observed with age, with advanced fibrosis peaking in the fifth decade. The proportion of individuals with advanced fibrosis was significantly greater in males than in females despite equivalent prevalence and intensity of schistosome infection. In addition, a positive association (P < 0.01) was found between periportal fibrosis and both hepatomegaly > or = 6 cm and splenomegaly. This study suggests that the natural history of schistosomiasis japonica in this hyperendemic community in China is marked by persistence of hepatomegaly and schistosome-induced periportal fibrosis in adults despite a decrease in the prevalence of infection.

Modeling blood/plasma concentrations in dosed feed and dosed drinking water toxicology studies

A computer model for predicting blood/plasma concentrations of test chemicals in dosed feed and dosed drinking water toxicology studies was developed. The model was constructed based on linear theory. The animal's feeding and drinking habits and the linear disposition kinetics of the test chemical obtained after a bolus gavage dose were built into the model. Blood/plasma concentrations of oxazepam and pentachlorophenol in dosed feed and dosed drinking water studies were predicted and compared with the experimentally determined data. The model proved highly reliable in predicting the blood/plasma concentrations of test chemical in dosed feed and dosed drinking water studies. The results suggest that if the kinetics of test chemicals fit a one-compartment model then bioaccumulation of the test chemical will occur in dosed feed or in dosed drinking water studies when absorption half-lives are less than 1.38 hr and elimination half-lives are longer than 5 hr. The extent of accumulation is mainly dependent on the elimination half-lives. For chemicals with absorption half-lives less than 1.38 hr and elimination half-lives less than 2 hr, the extent of bioaccumulation will be minimal. Blood/plasma concentrations of test chemicals in rats and mice will fluctuate daily and a quasi-steady state will be achieved after ad libitum exposure to dosed feed or dosed drinking water for approximately 4 days. If a daily 12-hr light cycle is used with the light cycle starting at 7:00 AM, the expected peak and trough blood concentrations in dosed feed studies will occur approximately in the early morning (5:00 AM) and in the late afternoon (4:00 PM), respectively. Similar results were obtained for dosed drinking water studies. The model should be applicable to dosed feed and dosed drinking water studies using other species.

Application of microencapsulation for toxicology studies. III. Bioavailability of microencapsulated cinnamaldehyde

The bioavailability of microencapsulated cinnamaldehyde (CNMA) was investigated in male F344 rats. Rats were gavaged with CNMA in corn oil using either microencapsulated or the neat chemical at doses of 50, 250, and 500 mg/kg. No differences between the two formulations at any of the doses were found in either CNMA blood concentration profiles or in the rate of urinary hippuric acid excretion. Both formulations showed a low bioavailability (< 20%) at 250 and 500 mg/kg. Regardless of the formulation used, oral gavage of CNMA significantly increased the urinary excretion of hippuric acid. About 75% of the dose of CNMA was metabolized to hippuric acid and recovered in the urine. The total amount of hippuric acid recovered in a 50-hr urinary collection correlated well with the CNMA dose. The data suggest that there was complete release of CNMA from the microcapsules and that microencapsulation of CNMA does not affect its bioavailability or its metabolism. Since CNMA microcapsules are stable in rodent diet, the microencapsulation of CNMA, and perhaps other labile chemicals, will prevent degradation and facilitate the testing of such compounds in toxicology studies.